Donald Trump has threatened to widen the scope of his trade tariffs, repeating his warning that the European Union – and potentially the UK – will face levies, even as he conceded that Americans could bear some of the economic brunt of a nascent global trade war.

It comes as Trump’s tariffs on Mexico, Canada and China, announced on Saturday, sparked retaliation from all three countries. Mexico and Canada have vowed levies of their own while China and Canada are seeking legal challenges.

Trump said on Sunday night that new tariffs on the EU would “definitely happen”, repeating previous complaints about the large US trade deficit with the bloc and his desire for Europe to import more American cars and agricultural products.

“It will definitely happen with the European Union, I can tell you that,” he told reporters. “I wouldn’t say there’s a timeline but it’s going to be pretty soon.”

Trump appeared to take a softer line on the UK, citing a good relationship with the prime minister, Keir Starmer, while saying tariffs still “might happen”. “The UK is out of line but I’m sure that one, I think that one can be worked out,” he said. “Well Prime Minister Starmer’s been very nice, we’ve had a couple of meetings, we’ve had numerous phone calls, we’re getting along very well, we’ll see whether or not we can balance out our budget.”

Before Trump’s latest threat to the EU, a spokesperson for the European Commission said on Sunday that the union would “respond firmly to any trading partner that unfairly or arbitrarily imposes tariffs on EU goods”. The EU responded to previous Trump tariffs by imposing duties on emblematic American goods made in Republican-leaning states, such as Harley-Davidson motorbikes, bourbon and orange juice.

The commission said it regretted Trump’s decision to impose tariffs on Canada, Mexico and China: “Tariffs create unnecessary economic disruption and drive inflation. They are hurtful to all sides.”

In Canada, the department of finance published a list of US products imported into Canada that it would target with a 25% retaliatory tariff starting on Tuesday.

The list shows products that will be hit in the first round of retaliatory tariffs by Canada starting on Tuesday, and amounts to $30bn Canadian dollars’ worth of goods (about US$20bn). The products include tobacco, produce, household appliances, firearms and military gear.

Canada is also preparing for a second, broader round of retaliatory tariffs in 21 days that will target an additional C$125bn (US$86bn) worth of US imports. The second list would include passenger vehicles, trucks, steel and aluminium products, certain fruits and vegetables, beef, pork, dairy products and more.

Claudia Sheinbaum, Mexico’s president, said her government will provide more details on the retaliatory tariffs she ordered on US goods on Monday. Sheinbaum, in a statement on Sunday, said she would announce details on her government’s “plan B” as she insisted that Mexico “doesn’t want confrontation”.

“Problems are not addressed by imposing tariffs, but with talks and dialogue,” she said. “Sovereignty is not negotiable: coordination yes, subordination no.”

Sheinbaum and the Canadian prime minister, Justin Trudeau, spoke by phone on Saturday after Trump’s administration imposed the new tariffs – 25% on goods from Canada and Mexico, with a lower rate of 10% for Canadian oil, and 10% on imports from China.

Trudeau’s office said in a statement that Canada and Mexico agreed “to enhance the strong bilateral relations” between their countries. Canadian officials have had extensive dialogue with their Mexican counterparts, but a senior Canadian official said he would not go as far as to say the tariff responses were coordinated.

“Now is the time to choose products made right here in Canada,” Trudeau posted Sunday on X. “Check the labels. Let’s do our part. Wherever we can, choose Canada.”

Trump acknowledged the sweeping tariffs he has imposed on Mexico, Canada and China could cause “short term” pain for Americans as global markets reflected concerns the levies could undermine growth and reignite inflation. Asian markets, cryptocurrencies and US and European stock futures slumped in early Asian trading on Monday.

“We may have short term some little pain, and people understand that. But long term, the United States has been ripped off by virtually every country in the world,” he said.

Late on Saturday, Trudeau said: “We’re certainly not looking to escalate, but we will stand up for Canada.” However, on Sunday evening, a senior government official from Canada briefing reporters in Ottawa on condition of anonymity said: “We will obviously pursue the legal recourse that we believe we have through the agreements that we share with the United States.”

The official said the Canadian government considered the move by Trump illegal and said it violated the trade commitments between the two countries under their free trade agreement and under the World Trade Organization. “If other legal avenues are available to us, they will be considered as well,” the official said.

Canada is the largest export market for 36 states, and Mexico is the largest trading partner of the US.

Canada and Mexico ordered the tariffs despite Trump’s further threat to increase the duties charged if retaliatory levies were placed on US goods.

China also said it would file a lawsuit against the tariffs. The imposition of tariffs by the US “seriously violates” World Trade Organization rules, China’s commerce ministry said in a statement, urging the US to “engage in frank dialogue and strengthen cooperation”.

Beyond the official response, people were already thinking of ways to cope with Trump’s decision, including by sharing suggestions on social media for alternatives to US products.

Canadian hockey fans booed the US national anthem on Saturday night at two National Hockey League games. The booing continued on Sunday at an NBA game in Toronto, where the Raptors played the Los Angeles Clippers.

One fan at the Raptors game chose to sit during the anthem while wearing a Canada hat. Joseph Chua, who works as an importer, said he expects to feel the tariffs “pretty directly”. “I’ve always stood during both anthems. I’ve taken my hat off to show respect to the American national anthem, but today we’re feeling a little bitter about things,” he said, adding that he will start to avoid buying US products.

In the streets, people in Mexico were trying to absorb the announcement on Sunday, although some in the capital acknowledged that they were unaware of the measures.

In the border city of Mexicali, across from Calexico, California, some people were concerned about the wider implications of a trade war.

Driver Alejandro Acosta says that he crosses the border weekly in his truck to deliver vegetables to US companies. He said he fears US businesses in the Mexicali Valley will no longer want to operate in Mexico and they will move to the US.

“If they raise taxes on the factories here, jobs may also decrease,” he said.