"Because it's very possible that [Mr] Putin lied to them the same way that he lied to Europeans and others," Mr Sullivan said.

In response, a spokesman for the foreign ministry in Beijing, Zhao Lijian, said the US was spreading disinformation.

He added that China's stance had always been consistent and that China was playing a constructive role in promoting talks. 

Mr Sullivan is due to meet Yang Jiechi, a member of China's top decision-making body, the Politburo, and the head of the Central Foreign Affairs Commission, on Monday in Rome.

Reuters news agency quoted a US official as saying that during the meeting, Mr Sullivan would spell out the consequences and isolation China would face if it increased support for Russia.

China has so far refrained from condemning Russia for the invasion and has said Moscow's "legitimate security concerns" should be taken seriously.

But Beijing at the same time has expressed "unwavering support" for Ukraine's sovereignty. It has also called for peace and has said it is ready to help end the war through diplomacy. Several countries have urged China to do more to stop Russia's invasion. The EU and US help Ukraine, China helps Russia; if that's how this goes, then it's a delineation that will make the war in Ukraine an even more consequential one.