Trump declares national emergency at border in first speech to nation

President Donald Trump has proclaimed "America's decline is over" as he vowed to act swiftly through sweeping executive action, including declaring a national emergency at the US-Mexico border.

In his inaugural address, Trump said he is "confident and optimistic" as he returns to the White House with "a mandate to completely and totally reverse a horrible betrayal," referring to the last four years under his predecessor Joe Biden.

Following the ceremonial peaceful transfer of power, Trump said he planned to sign a series of executive orders to crack down on the border, boost domestic energy and ending government-mandated diversity programmes.

"The golden age of America begins right now," he said from the US Capitol Rotunda, where the ceremony had been moved due to the freezing temperatures outside.

Trump outlined a number of steps he plans to immediately take, including sending troops to the border, declaring some gangs and drug cartels as foreign terrorist organizations and re-instating the controversial Remain in Mexico that requires that migrants wait for their asylum proceedings on the Mexican side of the border.

"All illegal entry will immediately be halted," he said, adding that his administration will "begin the process of returning millions and millions of criminal aliens back to the places from which they came."

"I have no higher responsibility than to defend our country from threats and invasions," Trump added.

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Earlier, incoming Trump administration officials outlined dozens of executive orders the president-elect planned to take when he officially takes office, including 10 focused on what one official described as "common sense immigration policy".

Officials also said that Trump plans to end birthright citizenship, meaning that the children of undocumented migrants living in the US will no longer automatically be considered US citizens.

Birthright citizenship, however, is enshrined in the US constitution and would require a two-thirds vote in both chambers of Congress to change. The official provided no further detail on how Trump plans to accomplish this.

In Trump's speech - the first of his second administration - he also promised a "complete overhaul" of the US trade system and the declaration of a National Energy Emergency, which officials said earlier would address the high costs of energy for consumers.

While Trump promised to "tariff and tax foreign countries to enrich our citizens", incoming officials said that no new tariffs would be announced on Inauguration Day, despite being a central part of the incoming president's economic vision.

Trump had previously said he would impose new tariffs on goods entering the US from Canada, Mexico and China on his first day in office.

His fiery remarks also included a promise to rename the Gulf of Mexico as the "Gulf of America", as well the tallest mountain in North America, Denali, to Mount McKinley - its name until it was changed by President Barack Obama in 2015.

He also repeated promises to "take back" the Panama Canal, which he claims is treating US ships "unfairly" and being operated by China.

"We didn't give it to China. We gave it to Panama," he said. "And we're taking it back."

Incoming officials also said that Trump plans to "end DEI [diversity, equity and inclusion" inside the government, and make it official policy that the US recognises two sexes - male and female.

Trump officially became president at noon local time (1700 GMT) at the US Capitol. He was expected to begin signing orders shortly thereafter.

The inaugural address will be followed by a luncheon, parade and a series of inaugural balls in the evening.

About 20,000 people are expected at the parade, which was moved inside to the Capital One Arena over the weekend due to concerns over frigid temperatures that swept across Washington DC.

The crowd is just a small fraction of the approximately 220,000 ticketed guests who were expected to watch the event from the grounds of the US Capitol.

On Monday morning, a desk had been set up in the centre of the arena - which some have speculated could be used to sign executive orders in front of his supporters.