U.S. president-elect Donald Trump criticized Ukraine's use of U.S.-supplied missiles for attacks deep into Russian territory in a Time magazine interview published on Thursday, comments that suggest he could alter U.S. policy toward Ukraine.

"It's crazy what's taking place. It's crazy. I disagree very vehemently with sending missiles hundreds of miles into Russia. Why are we doing that? We're just escalating this war and making it worse. That should not have been allowed to be done," Trump said in an interview to mark his being named Time's Person of the Year.

U.S. President Joe Biden last month lifted the U.S. ban on Ukraine using U.S.-supplied longer-range missiles for strikes deep inside Russia, his latest attempt to boost Kyiv in its battle to repel a Russian invasion force from his country.

The decision came after pleas from Ukrainian President Volodymyr Zelenskyy. The White House cited Russia's deployment of 15,000 North Korean troops along the battlefront as the main reason why Biden changed his mind.

Few details on Trump plan to end conflict

Trump has said he would like to bring a quick end to the nearly three-year-old war, but has been cagey on the details. He told Time he had a "very good plan" to help, but that if he reveals it now, "it becomes almost a worthless plan."

Pressed on whether he would abandon Ukraine, Trump said, "I want to reach an agreement, and the only way you're going to reach an agreement is not to abandon."

He said the entry of North Korean troops into the picture was a "very complicating factor."

Trump, who takes office on Jan. 20, met last weekend with Zelenskyy and French President Emmanuel Macron in Paris. Trump's promise to end the conflict swiftly has raised concerns in Kyiv that it could be largely on Moscow's terms.

Sources told Reuters that Zelenskyy used the meeting to explain Ukraine's need for security guarantees in any negotiated end to the war with Russia. He has long sought NATO membership.

'Staggering' death tolls in war: Trump

Trump told Time that the number of people dying in the conflict, especially in the last month, was "staggering."

"I'm talking on both sides. It's really an advantage to both sides to get this thing done," he said.

The war is entering what some Russian and Western officials say could be its final and most dangerous phase as Moscow's forces advance at their fastest pace since the early weeks of the conflict.

Russia fired a hypersonic ballistic missile known as the Oreshnik at the Ukrainian city of Dnipro on Nov. 21. Russian President Vladimir Putin cast the move as a response to Ukraine's first use of U.S. ATACMS ballistic missiles and British Storm Shadows to strike Russian territory with Western permission.

WATCH | Putin must be defeated, former Ukrainian leader says: 

Defeating Putin is the only way to stop the war: former Ukrainian president

Petro Poroshenko, former Ukrainian president, discusses what a second Trump U.S. presidency could mean for the war in Ukraine.

Washington says more deliveries of U.S. air defence exports to Ukraine are on the way to the country.

The United States last Saturday unveiled a $988-million US aid package of new arms and equipment to Ukraine.

Asked whether he had spoken to Putin since his election, Trump declined to answer, saying, "I can't tell you. I can't tell you. It's just inappropriate."

Shortly after Trump's election victory, Putin publicly offered congratulations to the U.S. president-elect and praised Trump's "brave" character in the wake of a failed assassination attempt this past summer.