Trudeau now takes a moment to speak directly to the American public.

"We don't want this," the Canadian prime minister tells them, "but your government has chosen to do this to you."

He adds that markets are down this morning, and warns Americans that inflation will rise in the US.

Trudeau also accuses Trump of choosing to put American jobs at risk at "thousands of workplaces" that succeed because of materials or consumers from Canada.

Prime Minister Trudeau says Canada plans to challenge the US's "illegal actions" by filing dispute resolution claims against US tariffs at the World Trade Organisation, saying it is a violation of a free trade agreement that exists between Canada and the US.

Canada will keeps its tariffs on US good in place until the US removes theirs, Trudeau adds, saying Canada is considering other options to respond other than retaliatory tariffs if Trump does not desist.

"Canadians are reasonable, and we are polite, but we will not back down from a fight, not when our country and the wellbeing of everyone in it is at stake," Trudeau says.

The outgoing Canadian prime minister adds both the US tariffs and the Canadian response came into effect in the early hours of the morning.

Canada will be implementing 25% tariffs against $155bn worth of American goods, he says, starting with tariffs on $30bn worth of goods immediately, and tariffs on the remaining $125bn worth of goods in 21 days.

Canadian PM Justin Trudeau has just arrived and reacts to America's new tariffs, which hours ago came into force.

"Today the United States has launched a trade war against Canada," Trudeau says. "Its closest partner and ally, its closest friend."

He says Washington is, at the same time, talking about working with Vladimir Putin - someone Trudeau calls a "murderer and a dictator".

"Make it make sense," Trudeau adds.

We said a little while ago that we were expecting to hear from Canada's PM Justin Trudeau at around 10:30 local time (15:30 GMT) - but we're yet to hear from him.

The scene is set with a microphone in place, six Canadian flags behind it and photographers waiting to the side.

As soon as Trudeau appears, we'll begin bringing you what he says.

Natalie Sherman
New York business reporter

Businesses in the US were already bracing for blowback, after several provinces across Canada, including Ontario, Manitoba and Nova Scotia, said last month they would ban sales of US alcohol from their shelves if the tariffs moved forward.

On Tuesday, the website for the Liquor Control Board of Ontario, a government-owned company that is one of the world’s biggest buyers of alcohol, was down, as it took steps to remove US products following the ban.

The US spirits industry counts Canada as its second largest export market after the EU, and the move will hit US-made drinks such as bourbon and whiskey. Not coincidentally, they are known for being produced in Kentucky, home to former Republican Senate leader Mitch McConnell.

Canada and other countries adopted a similar strategy during Trump’s first term to try to bring pressure to bear on Republicans, and curb Trump’s trade actions. But whether it will deliver the same punch this time around is an open question.

McConnell is set for retirement and Trump’s grip on the party has tightened.

While we wait to hear from the Canadian prime minister, Donald Trump has been posting on his Truth Social platform.

In one post, he says: "IF COMPANIES MOVE TO THE UNITED STATES, THERE ARE NO TARIFFS!!!"

It comes after comments he made yesterday from the White House, in which he said there was "no room left for Mexico and Canada" and that tariffs would take effect from today.

"What they'll have to do is build their car plants, frankly, and other things, in the United States, in which case they have no tariffs," he added - similar to what he's now posted on social media.

The car sector is one that could be badly affected by the new tariffs regime.

Car parts may cross the US-Canada border several times during the manufacturing process, and so might be taxed on multiple occasions - take a look at the graphic below:

We're expecting to hear from Canadian Prime Minister Justin Trudeau at around 10:30 local time (15:30 GMT).

He'll be speaking following the US's tariffs on Canada, China and Mexico coming into place - and for the first time since his statement announcing 25% taxes on billions of dollars' worth of US goods.

You'll be able to watch Trudeau speak when the time comes, and we'll bring you the key takeaways too.

Natalie Sherman
New York business reporter

The US stock market has just opened for trading.

Shares have opened lower, with the S&P 500 - which tracks 500 of America’s biggest companies - down more than 0.8%.

Shares swooned yesterday afternoon when President Donald Trump said the tariffs would be going ahead, with the S&P down more than 1.7%.

Markets will be closely watched today, as a gauge of how serious these tariffs are and what economic risks they might carry.

Meanwhile, European stock markets have also sank - Paris was down 1.9% while Frankfurt shed 2.9% and Milan was down by more than 3.0% at around 14:00 GMT.

Vanessa Buschschlüter
Latin America and Caribbean digital editor

The reporters gathered at the daily news conference, held by Mexico's president in Mexico City, were expecting to hear how her government plans to respond to the US tariffs.

And while Claudia Sheinbaum said Mexico will impose "tariff and non-tariff measures", she didn't elaborate what they would be, instead saying that they would have to wait for further details until Sunday - when she plans to announce them in a public speech.

Sheinbaum's statement went over a lot of points she has made over the past days; she even repeated the slogan she has often used when talking about Mexico's relationship with the US: "Co-operation and co-ordination, yes, subordination, no".

And while she went into some detail listing her government's accomplishments in the fields of security and the battle against fentanyl trafficking, what most of those tuned in to her news conference wanted to hear today were specifics about how Mexico will retaliate.

Claudia Sheinbaum says she will announce Mexico's retaliatory tariffs against the US on Sunday.

We'll bring you more on this in our next post.

Image source, Reuters

Sheinbaum says the US's decision to continue with their tariffs on Mexico comes "despite our work against gangs and fentanyl".

She also accuses the White House of publishing an "offensive" statement against Mexico last night, when Donald Trump - among other things - told reporters at the White House there was "no room left for Mexico or for Canada" in these negotiations.

The US has "no justification" for this decision, she goes on - adding that Mexico wants respect.

No retaliatory measures have been announced.

President Claudia Sheinbaum is currently delivering a statement on Mexico's response to the US's 25% tariffs on goods being imported to the US.

Earlier, she said "we need composure, serenity, and patience" - and that Mexico had contingency plans in place, but didn't outline what they were.

The speech is being filmed, but we don't currently have access to the feed. We'll bring you any key lines in our next few posts.

Nick Marsh
Asia Business Reporter, Singapore

Exports are key component of China's economic growth. They account for around a fifth of the country's wealth. Of those exports, around 15% go to the US which is more than any other country.

But in the past couple of years exporting has grown even more important for China's economy. That's because its own domestic market, which makes up the bulk of the country's growth, has been so sluggish.

Households just aren't spending like they used to, partly because a lot of people's wealth is tied up in real estate, where value has plummeted.

In fact, while the rest of the world has dealt with inflation, China has had a problem with decreasing prices - deflation.

Factories are still producing goods and these goods need to be sold somewhere. It has led to what critics call "overcapacity" and accusations China is "dumping" - selling its products on to other countries at prices so cheap that they undercut the local competition.

This may lead to a vicious circle for China: the more it needs to export to make up for poor domestic demand, the more aggrieved other countries may become and the more tempted they will be to impose tariffs of their own on Chinese goods.

Lily Jamali
North America technology correspondent

Americans are bracing for a price shock thanks to President Trump’s tariffs.

The vast majority of our consumer electronics are imported. It’s been the talk of the tech industry for months now.

In the lead-up to January’s CES, the massive expo held every year in Las Vegas, the Consumer Technology Association put out an eye-popping estimate: smartphones could soon cost Americans about $213 more, on average — a hike of more than 25%.

That’s because smartphone makers are likely to pass on the cost of tariffs to customers. It’s rarely companies or foreign governments that pay the price.

It's no wonder Apple CEO Tim Cook has been so busy courting Trump lately. Last month, the iPhone maker announced a $500 billion investment in its US operations over the next four years.

Trump said his tariffs are the reason, although the company was already working to broaden its supply chain in response to the pandemic.

China is hitting Trump where it could hurt - his supporter basepublished at 12:50 Greenwich Mean Time 4 March

12:50 GMT 4 March

Laura Bicker
China correspondent

This is the second round of tariffs the world’s two largest economies have imposed on each other since February.

This time China is hitting Donald Trump where it has the potential to hurt - by targeting farmers, who are some of his core supporters.

This country is one of the biggest consumers of US produce, such as chicken, beef, pork and soybeans, and now all those products will face a 10-15% tax from 10 March.

The foreign ministry says China will "not yield" to what it describes as US bullying, but these latest measures are bound to sting.

The cumulative 20% tax on all Chinese goods comes on top of a slew of tariffs Trump imposed in his first term on tens of billions of dollars of Chinese imports.

China's population is already concerned about a sluggish economy. House prices are still falling, and youth unemployment remains stubbornly high.

The growing threat of a trade war with the US could prompt more money worries for businesses and consumers at a time when the Communist Party wants people to spend to help the economy to grow.

For those of you just joining us, welcome. As of midnight in Washington DC, President Donald Trump's tariffs against Canada, Mexico and China - three of the US's biggest trading partners - took effect, sparking retaliatory action.

Here's what you need to know:

• The US announced tariffs of 25% on imports from Canada and Mexico, as well as a fresh 10% levy on Chinese products
• In response, Canada announced 25% tariffs against the US on appliances, household items and products such as orange juice, wine, spirits, beer and coffee
• China has said it will place tariffs of up to 15% on a range of American agricultural and food products - Beijing said it would fight to the "bitter end" if the US continues its trade actions, urging a return to negotiations
• Mexico is also expected to announce its own response later today, but President Claudia Sheinbaum has already said her country had contingency plans
• Stock markets around the world have fallen following the introduction of tariffs - with analysts warning they could drive up prices for American households and have a knock-on effect for consumers around the world
• And the EU has condemned the tariffs on Canada and Mexico, saying they were a threat to economic stability

Image source, Getty Images

Image source, Getty Images

Responding to US tariffs placed on Canada and Mexico, the European Union (EU) has said the move by President Trump risks "disrupting global trade".

"These tariffs threaten deeply integrated supply chains, investment flows and economic stability across the Atlantic," says European Commission spokesman Olof Gill.

He adds the EU will stand "firmly against protectionist measures" which undermines "open and fair trade".

European countries also face extra taxes, with 25% tariffs for aluminium and steel imports due to kick in worldwide on 12 March.

Gill adds the EU wants the US "to reconsider its approach and work towards a cooperative, rules-based solution that benefits all parties".

Tariffs are taxes charged on goods imported from other countries.

Companies which bring foreign products into the country have to pay the tax to the government, which normally ends up being a percentage of a particular item’s value.

For example: a 10% tariff means a product imported to the US worth $4 would face an additional $0.40 charge.

When President Trump was in power during his first term, he used the measure as a tool to punish China and pressure countries to renegotiate trade deals.

He says tariffs are a key part of his economic plans, claiming they will boost US manufacturing, protect jobs and grow the economy.

But some economists say it can make prices higher for US consumers, with companies passing on the cost of tariffs to customers.

• Read more on how tariffs work and which products could be affected