"We welcome the Chinese announcement that they want peace because that's what we always want to pursue in situations like this. But we also have to be clear that if there are any thoughts and efforts by the Chinese and others to provide lethal support to the Russians in their brutal attack against Ukraine, that that is unacceptable," Ambassador Linda Thomas-Greenfield told CNN on Sunday.

"That would be a red line," she said.

The ambassador's comments pertained to an unsubstantiated claim made by Secretary of State Antony Blinken on Sunday that China is "considering providing lethal support to Russia in the war against Ukraine," according to US intelligence. 

The US has been making evidence-free claims in relation to China arming Russia against Ukraine since the war began. In March of last year the New York Times reported that "Russia asked China to give it military equipment and support for the war in Ukraine after President Vladimir V. Putin began a full-scale invasion last month, according to U.S. officials." Then in April of last year NBC reported that this claim "lacked hard evidence" and was essentially just a lie the US government told the media "as part of an information war against Russia."