U.S. ambassador to U.N. warns China would be crossing a ‘red line’ if it provides lethal aid to Russia

China would be crossing a “red line” if it provided lethal aid to Russia in its war in Ukraine, the U.S. ambassador to the United Nations warned Sunday.

“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 said in an interview on CNN’s “State of the Union.”

“That would be a red line,” she said.

The Biden administration is prepared to compete with China and, "when necessary, to confront the Chinese,” Thomas-Greenfield said, adding: “And that’s what we’re doing. And that’s what we will continue to do to ensure that our national interests are always at the forefront."

The U.S. believes China may be providing nonlethal military assistance to Russia for use in Ukraine, and the administration worries Beijing is considering sending lethal aid, four U.S. officials familiar with the matter said in an exclusive report Saturday.

While China has provided some help to Russia, including parroting Russian disinformation campaigns and promoting Russian false pretexts for the war, this is more tangible assistance for Russian troops in Ukraine, sources familiar with the matter said.

The officials declined to provide specifics about the nonlethal military assistance, which they said could include gear for the spring offensive, such as uniforms or even body armor.

The Chinese embassy did not respond to a request for comment.

Secretary of State Antony Blinken met Saturday with a senior Chinese diplomat at the Munich Security Conference as tensions between the two countries mount over the suspected Chinese balloon the U.S. shot down this month.

A source familiar with the conversation said the possibility of China’s providing nonlethal military assistance or lethal aid to Russia was “an essential topic of conversation” at Blinken’s meeting with Wang Yi, the director of the Communist Party’s Central Foreign Affairs Office.

In an interview on NBC News’ “Meet the Press," Blinken said, "We're very concerned that China is considering providing lethal support to Russia in its aggression against Ukraine, and I made clear that that would have serious consequences in our relationship."

China has refrained from condemning the Russian invasion while being careful to avoid violating international sanctions.

Beijing is "trying to have it both ways,” Blinken said. “Publicly, they present themselves as a country striving for peace in Ukraine. But privately, as I said, we’ve seen already over these past months the provision of nonlethal assistance that does go directly to aiding and abetting Russia’s war effort.”

Blinken declined to go into details about what form the lethal aid could take, saying, "There are various kinds of lethal assistance that they are at least contemplating providing," which could "include weapons.”

This article was originally published on NBCNews.com