LONDON — Boris Johnson and Jeremy Hunt, the two contenders to be Britain’s next prime minister, condemned tweets by U.S. President Donald Trump but refused to say if they think they were racist.

Johnson, the favorite to succeed Theresa May, also said he wouldn’t support U.S.-led military strikes against Iran, as the transatlantic alliance again became the focus of the election to lead the U.K.’s governing Conservative Party at a time when U.K.-U.S. relations are already strained.

The two men were asked their views after Trump posted a series of tweets suggesting that four U.S. congresswomen, led by Alexandria Ocasio-Cortez of New York, should return to the “broken and crime infested places from which they came.”

Johnson said the tweets were unacceptable. “When you are the leader of a great multiracial, multicultural society, you simply can’t use that sort of language about sending people back,” he said.

Hunt, who has a Chinese wife and mixed-race children, said the comments were “totally offensive.”

“I have three half-Chinese children and they are British citizens,” Hunt said. “If anyone ever said to them ‘go back to China,’ I would be utterly appalled.”