The United States hit Russia's major oil companies with sanctions on Wednesday and accused the Russians of a lack of commitment toward ending the war in Ukraine, as Moscow conducted a major training exercise involving nuclear arms.

The new sanctions were unveiled one day after plans for a summit between US President Donald Trump and Russian President Vladimir Putin fell apart. Trump told reporters he cancelled the meeting because "it didn't feel right to me."

The US Treasury Department said Russia's two largest oil companies, Rosneft and Lukoil, were targeted in a bid to damage Moscow's ability to fund its war machine.

"Now is the time to stop the killing and for an immediate ceasefire," US Treasury Secretary Scott Bessent said. Oil prices extended gains after Bessent's comments, rising by more than US$2 a barrel.

For months, Trump has resisted pressure from US lawmakers to impose energy sanctions, hoping that Putin would agree to end the fighting. But with no end in sight, he said he felt it was time.

Trump's measure on Wednesday followed Britain's sanctioning of Rosneft and Lukoil last week.

A senior Ukrainian official said the step was “great news” and that the two Russian energy companies were among US sanctions targets proposed by Kyiv in the past.

The Russian embassy in Washington and the Russian mission to the United Nations in New York did not immediately respond to a request for comment on the sanctions.

The US president said, however, that he was still not ready to provide Ukraine with long-range Tomahawk missiles, which Kyiv has requested.

Talking to reporters as he met Nato Secretary General Mark Rutte, Trump said it would take the Ukrainians at least six months to learn how to use them.

Ahead of a meeting next week with President Xi Jinping in South Korea, Trump said he would like to see Xi use his influence on Putin to halt the fighting.

In a fresh show of force, the Kremlin released video showing General Valery Gerasimov, head of the General Staff, reporting to Putin on the drills.

Russia said it fired missiles from ground launchers, submarines and aircraft, including intercontinental ballistic weapons capable of striking the United States.

Russia's Defence Ministry said its long-range Tu-22M3 strategic bombers flew over the Baltic Sea, escorted at various points by fighter jets from foreign states. (Reuters)