Washington DC - US President Donald Trump was "unsurprised" after Russia resumed intense attacks on Ukraine, ending a cold-weather pause he personally requested from Vladimir Putin, the White House said Tuesday.

"I spoke with the president about it this morning, and his reaction was, unfortunately, unsurprised," Press Secretary Karoline Leavitt told reporters outside the West Wing.

"These are two countries who have been engaged in a very brutal war for several years, a war that have would have never started if the president were still in office," she added.

Republican Trump has repeatedly blamed his Democratic predecessor Joe Biden for Russia's 2022 invasion, saying Putin would not have launched it if he were in power.

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But Trump's promise to end the war within 24 hours of taking office through what he claims is a friendship with Putin has so far come to nothing, and he has expressed frustration with the Russian leader on several occasions.

Trump announced on Thursday that Putin had agreed to pause attacks on Kyiv for a week during a spell of freezing weather, and talked about the arrangement on Monday to reporters.

But the Kremlin said that the week-long pause in fact ended Sunday. Ukraine overnight reported the "most powerful" Russian attack this year on its battered energy facilities.

Trump's special envoy Steve Witkoff and son-in-law Jared Kushner would be in Abu Dhabi on Wednesday for "another round of trilateral talks" with Ukraine and Russia, Leavitt said.