Downing Street said that the White House had been aware of Starmer's trip and its objectives in advance and pointed out that Trump himself is due to visit China in April.
US President Donald Trump has it is "very dangerous" for close ally Britain to deal with China, as UK Prime Minister Keir Starmer is in the country for talks with President Xi Jinping aimed at resetting relations.
Trump made the remarks to reporters while attending the premiere of a documentary about his wife, First Lady Melania Trump.
Asked about the UK "getting into business" with China, Trump said "Well it's very dangerous for them to do that."
Starmer's visit to China is the first by a British premier since 2018 and follows a slew of Western leaders seeking a rapprochement with Beijing recently, seen by many as a pivot from an increasingly unpredictable United States.
In response to Trump's comments, Downing Street said that the White House had been aware of Starmer's trip and its objectives in advance and pointed out that Trump himself is due to visit China in April.
On Thursday, Starmer met with Xi and other Chinese officials and signed several cooperation agreements.
Canadian Prime Minister Mark Carney also visited China in mid-January and reached agreements on trade and tourism.
Afterward, Trump threatened to hit Canadian imports with 100% tariffs if Carney made further deals with Beijing, a threat the Canadian PM later dismissed as a negotiating tactic.
"It's even more dangerous, I think, for Canada to get into business with China. Canada is not doing well. They're doing very poorly, and you can't look at China as the answer," Trump said.
Meanwhile, Starmer arrived in China’s financial centre Shanghai on Friday in his bid to boost business opportunities for UK firms in the world's second-largest economy.
Starmer has brought more than 50 business leaders on his trip.
Starmer said on Friday that he had had "very good meetings" with Xi, that had provided "just the level of engagement that we hoped for."
"We warmly engaged and made some real progress, actually, because the UK has got a huge amount to offer," he said at the Bank of China in Beijing.