The so far vague accusations come from US Secretary of State Anthony Blinken.
He claimed this weekend that China is considering providing "lethal support" to Russia - such as weapons and ammunition.
- We have worried about that possibility since day one, said Blinken in an interview with CBS.
He said at the same time that such action would cause "serious problems" in the relationship between the US and China and that more information will be made public later.
NATO Secretary General Jens Stoltenberg says during a press conference on Tuesday with Ukrainian Foreign Minister Kuleba that he feels growing concern that China may have plans to support Russia with weapons in the country's war of aggression against Ukraine.
"Should not exert pressure"
China has hit back at the accusations, calling them "false".
It is the United States, not China, that has pumped weapons into the war through its support for Ukraine, Wang Wenbin, a spokesman for China's foreign ministry, said at a press briefing on Monday.
- We do not accept that the US points the finger at the relationship between China and Russia, even less that they exercise coercion or pressure.
High-ranking Chinese diplomat Wang Yi is due to visit Moscow shortly, and according to Kremlin spokesman Dimitriy Peskov, a personal meeting with President Putin is not out of the question.
Claims to want peace
China has emphasized during the war that it advocates a peaceful solution to the war.
At the same time, Beijing has not wanted to condemn the invasion and trade with Russia has continued on a large scale.
Recently, the American newspaper Wall Street Journal reported that China provided Russia with technology that could be used for military purposes.