US President Donald Trump has threatened to place an additional 10 percent tariff on Chinese imports on top of the 10 percent imposed earlier in February and said a 25 percent levy on Mexican and Canadian goods will take effect March 4.

"This would be an additional 10 percent [tariff] on China. …This would be 10 plus 10," Trump told reporters Thursday during a meeting with British Prime Minister Keir Starmer at the White House.

Trump made the announcement after accusing Canada and Mexico of not stemming illicit fentanyl entering the United States.

"Drugs are still pouring into our Country from Mexico and Canada at very high and unacceptable levels," Trump posted on Truth Social earlier Thursday.

"We cannot allow this scourge to continue to harm the USA, and therefore, until it stops, or is seriously limited, the proposed TARIFFS scheduled to go into effect on MARCH FOURTH will, indeed, go into effect, as scheduled."

US economists and trade groups said that any extra tariffs will likely hit American consumers the hardest.

Tiffany Smith, vice-president of global trade policy for the National Foreign Trade Council (NFTC) in Washington DC, told China Daily, "Adding new and expanded tariffs will harm working families."

In his first term, Trump in 2018 placed tariffs on $300 billion of Chinese-made goods sparking a trade war.

Former president Joe Biden maintained those original tariffs and increased levies on $18 billion of Chinese imports in September.

"We made tremendous amounts of progress because of those tariffs. China paid us hundreds of billions of dollars. Billions!" Trump said of his previous levies.

In early February, a 25 percent tariff that was set to go into effect on goods from Mexico and Canada was put on hold for a month after both countries vowed to send more troops to the border, and Canada appointed a fentanyl czar.

President Claudia Sheinbaum of Mexico sent 10,000 troops to the border and Sinaloa state, an alleged source of fentanyl trafficking.

The Canada Border Services Agency launched Operation Blizzard aimed at "intercepting illegal contraband arriving and leaving Canada, with a focus on fentanyl and other synthetic narcotics".

Mexico, Canada and China are the top three trading partners of the US, accounting for a third of goods imported and exported.

The three countries purchased more than $1 trillion of goods from the US and sent $1.5 trillion worth of exports in 2023, US government data shows.

"Putting tariffs on imports from Canada and Mexico risks undermining America's relationship with our closest trading partners and allies and has the potential to affect the price and availability of everything from avocados to automobiles," NFTC?President Jake Colvin said in a Feb 1 statement.

Out of nearly $4 trillion in goods and services imported in 2023, $448 billion was from China, according to US Census Bureau data.

Mexico is also a major source of food imports, sending $9.9 billion worth of vegetables and $11 billion worth of fruit and juices to the US in 2023, according to the US Department of Agriculture.

Mary Lovely, professor emeritus of economics at Syracuse University and senior fellow of the Peterson Institute for International Economics in Washington, told China Daily that tariffs will "take a larger share of income" from low-earning households.

Trump told a reporter who contended that China does not pay the tariffs but American importers and consumers do that, "I think they're paid for by the country."

Trump is trying to get Americans to shop at home and for manufacturers to produce more domestically.

Lovely said that politicians often tout tariffs as positive as they "cling to the belief that it creates jobs in the US".

In response, China's Ministry of Finance announced tariffs in February on US coal and liquefied natural gas, agricultural machinery such as farm equipment, large-displacement cars and pickup trucks.

Mexico has sent a trade delegation to the US to negotiate an agreement that will prevent tariffs.

"We are working together to reach agreements before the fatal dates," Mexico's Deputy Foreign Trade Minister Luis Rosendo Gutierrez told Reuters.

Canadian Prime Minister Justin Trudeau said that Canada "will have an immediate and extremely strong response" if US tariffs go ahead.

At least $2.5 billion worth of goods are traded with Canada per day, or $800 billion a year.

The US president confirmed another plan for further reciprocal tariffs globally starting in April due to "unfair" treatment of US companies like Apple. It would come after an investigation by his agencies.

Hundreds of billions of dollars of goods go between the European Union and the US. "We're going to have reciprocal tariffs," Trump said about the EU. "Whatever they charge us, we're going to charge them."