In short: yes he can, says Scott Lucas, professor of US and international politics at the Clinton Institute at University College Dublin.

Among the raft of executive actions that Trump signed yesterday was an order to begin the process of withdrawing the US from the World Health Organization, and leaving the Paris climate agreement.

“He can withdraw the US from participation in our international programmes,” Lucas says.

“As long as there is not a treaty that locks the US into it, you do not need congressional approval for this", he explains. That means that the US is now on its way to formally exiting the WHO and the Paris climate agreement.

Image source, EPA

News agencies are watching closely as US President Donald Trump takes office for a second time, and the returning president is leading coverage on front pages around the world.

We've rounded up some that were published this morning.

Image source, The Wall Street Journal

Image source, The Daily Telegraph

Image source, The i paper

Image source, The Globe and Mail

A little more now from Robert Wilkie, the head Trump's transition team in the Pentagon, who appeared a little earlier on the Today programme.

He's been talking about Trump's approach to the war in Ukraine.

Wilkie says Trump will phone Russian President Vladimir Putin and tell him to stop the war

He adds that Trump will tell Ukraine's president Zelensky that he hasn’t done enough "by not calling to the colours the largest segment of your population", continuing that Zelenskyy has left out "males in the population who provide the muscle and the strength".

If Putin resists Trump's calls to end the war, Wilkie says, one of Trump's executive orders "will unleash American energy power".

"The flow of American liquified natural gas to Europe will begin," Wilkie says, "and the US presence on the world oil market will drive price of oil down – that will bankrupt the Russian economy. That is going to put an incredible stain on Putin’s wartime economy."

Speaking a little earlier on BBC's Today programme, Robert Wilkie, the Veterans Secretary in Donald Trump's first administration, says that Trump will want the UK to spend more on defence.

“The world is stronger when the British military is more capable," he says.

Asked if the Chagos Islands is an "early test" for the defence relationship between Trump and UK government, Wilkie replies "absolutely. Diego Garcia has been a vital strategic node for the US and UK for decades".

The UK government had been committed to returning the islands to Mauritius. But Trump does not want the UK to do so, and London's decision to cede control of the islands "could infringe on that special relationship" between the UK and the US, Wilkie says.

For background: The UK took control of the Chagos Islands from Mauritius in 1965, and announced in October it would cede sovereignty but maintain control of the base on the largest island Diego Garcia under a 99-year lease.

Image source, Reuters

On the first day of his second term, Trump referred to North Korea as a "nuclear power" and asked US troops stationed in South Korea how the North's leader, Kim Jong Un, was doing.

His "simple" way of referring to the Korean peninsula could have repercussions for Washington's ally, Seoul, says Leif-Eric Easley, a professor at Ewha University.

"For Trump, it is a simple fact that North Korea has nuclear weapons, and it is straightforward that states with nuclear weapons must get along to avoid war," Easley says.

"The danger for South Korea is that longstanding alliance efforts for military deterrence could take a back seat to Trump’s personalistic diplomacy. Any uncoordinated policy change regarding North Korean denuclearization could leave Seoul vulnerable to Pyongyang’s coercion," he adds.

Lily Jamali
North America Technology Correspondent

President Donald Trump has signed an executive order granting TikTok a 75-day extension to comply with a law that requires a sale or ban of the platform.

In comments made to reporters as he signed the directive in the Oval Office on Monday, Trump said, "I tell you what. Every rich person has called me about TikTok."

The executive order directs the US attorney general not to take any action to enforce the act on behalf of the United States during that time.

The reprieve would "permit my Administration an opportunity to determine the appropriate course of action with respect to TikTok," it states.

Former President Joe Biden signed the divest-or-ban law last year. It was passed on a bipartisan basis by Congress on national security grounds stemming from TikTok’s Chinese ownership.

Trump said the timing of the ban - which had been due to kick in on the day before he took office - was "unfortunate" and interfered with his ability to "assess its national security and foreign policy implications."

The order places Trump at odds with the Supreme Court which unanimously upheld the law on Friday and many members of Congress - including several Republicans.

TikTok went dark on Saturday evening before returning online mid-Sunday.

American users accessing the app were then greeted with a notification stating: “We are fortunate that President Trump has indicated that he will work with us on a solution to reinstate TikTok once he takes office. Please stay tuned!”

When asked by a reporter why he's had a change of heart since trying to ban TikTok in 2020, Trump responded: "Because I got to use it."

Image source, Getty Images

More now on one of the orders signed by President Donald Trump in the Oval Office earlier.

Trump has moved to dismantle a longstanding interpretation of the 14th Amendment, ordering federal agencies to deny birthright citizenship to children of parents who are unauthorised immigrants or temporary visa holders.

Agencies have been given 30 days to implement the order - although it is likely to face swift legal challenges.

Trump does not intend to waste a moment of his presidencypublished at 07:29 Greenwich Mean Time 21 January

07:29 GMT 21 January

Sarah Smith
North America editor, reporting from Washington DC

This barrage of presidential orders amounts to a brute force attack on the established order. President Trump is rewriting the rules – across the board.

Demonstrating that he intends to use all the power of the Oval Office to try to deliver the radical change he promised to bring to America

President Trump cannot do everything he wants simply by signing his name. The order to end the right of anyone born in the US to become an American citizen, for instance, will be challenged in court. Many of his other aims will require legislation to be passed by congress.

But with a stroke of his pen he has taken the US out of the Paris climate accords, withdrawn from the World Health Organization and declared a national emergency along the Mexico border

And he has demonstrated beyond doubt that he does not intend to waste a moment of his presidential term. He means to be a transformational president, and he has started already

Image source, EPA

Trump has signed a raft of executive actions on his first day as president.

Here's a look at the measures he enacted on day one.

• Withdrawing the US from the Paris climate agreement
• Kickstarting the process of exiting the World Health Organization
• Declaring a "national emergency" on the country's southern border

• "Defending women from gender ideology" and "restoring biological truth to the federal government"

• Pardoning those involved in the January 6 Capitol riots
• Holding "former government officials accountable for election interference"
• Ordering the federal government to restore freedom of speech and prevent government censorship of free speech
• Establishing the "Department of Government Efficiency" (Doge), which is an advisory board and not an official government department

• A regulatory freeze preventing bureaucrats from issuing any more regulations until the administration has full control of the government

• Directing every department and agency in the federal government to address the cost-of-living crisis
• An action Trump says will temporarily prevent a ban on TikTok coming into force

US President Donald Trump says he is "not confident" that the Gaza ceasefire deal will be upheld.

Responding to questions from a reporter a littler earlier, Trump said: "That's not our war, it's their war. But I'm not confident."

However, he adds that Hamas had been "weakened" adding that Gaza looked like a "massive demolition site".

The former real estate mogul says that "beautiful things could be done" with Gaza if the plan moves ahead, telling the reporter: "It's a phenomenal location on the sea ... You know, everything's good."

Multi-billionaire Elon Musk has drawn controversy at a post-inauguration event in Washington, where he made two gestures to the crowd, sweeping his hand from his chest upwards.

Onlookers have described the gesture as a Nazi salute. We have a video of the moment below.

On his social media platform X, Musk has called the criticism a "tired" attack.

"Frankly, they need better dirty tricks. The 'everyone is Hitler' attack is sooo tired", he writes.

Image source, Reuters

Good morning to our readers in the UK who are just starting their day.

Donald Trump has capped off Inauguration Day by speaking and dancing at three different balls, accompanied by his wife Melania.

It was a packed day for Trump, as he returned to the White House as the 47th US president. Here are the key events:

• Trump issued nearly 1,600 pardons for those involved in the events of 6 January 2021, many of whom are expected to be freed within hours
• He signed a flurry of executive orders and decrees aimed at cracking down on immigration, some of which are expected to be met with legal challenges
• As in his first term, Trump vowed to withdraw the US from the Paris climate agreement and signed an executive order to begin the process of withdrawing the US from the World Health Organization
• He signed an order granting TikTok a 75-day extension to comply with a law that requires a sale to avert a ban of the platform.

You can re-watch the key moments of the day, including Trump's air kiss with the hat-wearing first lady, here. Here is a collection of the day's best images as Trump took his oath. And here is our analysis of Trump's inaugural address, where he promised a new "Golden Age" for America.

Image source, Reuters

For the first time as the 47th US president, Trump has fired off a late-night social media post punctuated with his catch phrase from reality television show The Apprentice.

On his own social media platform Truth Social, Trump said he was "actively in the process of identifying and removing" over a thousand Biden appointees who are "not aligned with our vision to Make America Great Again".

He named four officials: Jose Andres from the President’s Council on Sports, Fitness and Nutrition, Mark Milley from the National Infrastructure Advisory Council, Brian Hook from the Wilson Center for Scholars, and Keisha Lance Bottoms from the President’s Export Council.

"YOU'RE FIRED!" Trump wrote.

As we've been reporting, President Trump has pardoned nearly everyone charged with participating in the Jan 6 attacks on the US Capitol.

Our correspondent Emma Vardy is outside the jail housing the defendants, where many people have gathered to await their release, though it's unclear when this might happen.

The Starlight Ball, the third and final of Trump's inaugural balls, is happening now - though the event is closed to the press.

The Trump campaign's biggest donors are expected at the ball at Union Station, where singer-songwriter Gavin DeGraw is performing.

Emerging on social media are videos taken by attendees of the ball, where Trump and Vance again danced with their partners on stage.

Image source, Getty Images

Among US elite circles, old and new, in the Capitol Rotunda on Monday was former vice-president Mike Pence.

He was one of the first to be introduced during today's inauguration - eight years after his own inauguration as vice-president.

And it was four years ago since there were calls by Trump supporters for Pence to be hung during 6 January riots.

In March 2023, Pence said Trump's words "endangered [his] family and everyone at the Capitol that day, and I know history will hold [him] accountable.”

He unsuccessfully ran for the Republican presidential nomination in 2024.

Earlier today, he wrote on X: "This is a day when every American does well to celebrate our democracy and the peaceful transfer of power under the Constitution of the United States".

The BBC's analysis editor Ros Atkins looks at Trump's newly-announced policies on gender and diversity.

Senate Democratic leader Chuck Schumer has said in a statement that individuals who were convicted in the 6 January Capitol attack should not have been pardoned, "whether they committed violence or not".

"They unlawfully broke into the Capitol to stop the peaceful transfer of power. What they did is a serious crime," Schumer said. "Donald Trump is ushering in a Golden Age for people that break the law and attempt to overthrow the government."

In case you missed it, about 1,500 January 6 rioters - whom Trump and his supporters have described as "hostages" - were pardoned in an executive order signed by Trump today, shortly after he was sworn in.

As Trump moves to exit the stage, he pumps his fists as the Village People perform YMCA - the disco hit that has become something of an anthem for Trump and his supporters.

Walking behind Trump, Vance waves and gives the thumbs-up sign to the side.

Members of Trump's family are following behind, some of them also dancing to the song.

Read more: How YMCA became Donald Trump's unlikely anthem

Trump repeats several talking points from his events earlier this evening.

He says the US will rapidly ramp up extraction of "the liquid gold" under the audience's feet, referring to oil. He talks about the definition of gender, and pledges to increase the strength of the military.

"We just want a great country," he says.

He also teases that there will be more announcements to come, before ending the brief address.