President-elect Donald Trump said in an interview published Thursday that he disagrees "very vehemently" with Ukraine firing American-supplied missiles deep into Russia.
But Trump insisted he would not abandon Ukraine as U.S. support for Kyiv would be key leverage in efforts to bring the war to a close.
Outgoing President Joe Biden's administration has supplied long-range ATACMS missiles to Ukraine, which can penetrate inside Russia, provoking angry retaliation from Moscow which has responded with its new hypersonic missile.
"I disagree very vehemently with sending missiles hundreds of miles into Russia. Why are we doing that?" Trump said in an interview with Time Magazine which named him its "person of the year" on Thursday.
"I think it's a foolish decision."
ATACMS missiles have a maximum range of 190 miles, according to publicly available data.
The interview was conducted before Thanksgiving and Trump's high-profile meeting with Ukrainian President Volodymyr Zelenskyy brokered by France's president on the sidelines of the reopening of Notre Dame cathedral.
"We're just escalating this war and making it worse," he added.
Pressed on his support for Ukraine, which has been lukewarm with the Republican questioning the cost of backing Kyiv, Trump said he would use Washington's backing as leverage to bring the war to a close.
"I want to reach an agreement and the only way you're going to reach an agreement is not to abandon."
Russian news agencies have jumped on Trump's comments, drawing attention to the Republican's apparent criticism of Kyiv's approach.
White House spokesman John Kirby said he was "not going to get into a back and forth" with Trump's incoming administration over the remarks.
"All I can do is reiterate what President Biden's policy and guidance has been, and that is to do everything we can ... so that if and when this comes to some sort of negotiation, that President Zelensky is in the best possible position," he told reporters.