THE US says China is considering supplying weapons and ammunition to Russia for the Ukraine war - a claim strongly denied by Beijing.

US Secretary of State, Antony Blinken said Chinese firms were already providing "non-lethal support" to Russia and new information suggested Beijing could provide "lethal support".

Such an escalation would mean "serious consequences" for China, he warned.

Beijing said the claims were false and accused Washington of spreading lies.

"We do not accept the United States' finger-pointing on China-Russia relations, let alone coercion and pressure," China's foreign ministry spokesman Wang Wenbin said this week.

China has also denied reports that Moscow has requested military equipment.

Chinese President Xi Jinping is an ally of Russian President Vladimir Putin and is yet to condemn Russia's invasion of Ukraine - but he has sought to remain neutral in the conflict and has called for peace.

Blinken was speaking to CBS News after he met China's top diplomat, Wang Yi, on Saturday at the Munich Security Conference.

He said that during the meeting he expressed "deep concerns" about the "possibility that China will provide lethal material support to Russia".

"To date, we have seen Chinese companies... provide non-lethal support to Russia for use in Ukraine. The concern that we have now is based on information we have that they're considering providing lethal support," he said.

He did not elaborate on what information the US had received about China's potential plans. When pressed on what the US believed China might give to Russia, he said it would be primarily weapons as well as ammunition.

Blinken told CBS that "of course, in China, there's really no distinction between private companies and the state".

If China provided Russia with weapons, that would cause a "serious problem for us and in our relationship", he added.

Relations between Washington and Beijing were already poor after the US shot down an alleged Chinese spy balloon in early February. Both sides exchanged angry words, but equally both sides appeared embarrassed by the incident and seemed ready to move on.

But if China were to deliver weapons to help Russian forces in Ukraine, then US-Chinese relations would deteriorate much more severely.

It would be the most "catastrophic" thing that could happen to the relationship between the two giants, said top Republican senator Lindsay Graham.

"It would be like buying a ticket on the Titanic after you saw the movie," he told ABC News. "Don't do this."

Blinken's warning seems to be clearly designed to deter China from doing that.

He also said the US was worried about China helping Russia evade Western sanctions designed to cripple Russia's economy. China's trade with Russia has been growing, and it is one of the biggest markets for Russian oil, gas, and coal.