President Joe Biden’s top national security adviser said Sunday that the White House had not yet seen China provide Russia with lethal assistance in its war on Ukraine and warned Beijing that doing so would be against their interests.

“We have not seen China yet provide military equipment to Russia for purposes of fighting in the war in Ukraine. We haven’t seen it yet,” White House national security adviser Jake Sullivan said on NBC News’ “Meet the Press.”

“We’re continuing to watch. We’ll stay vigilant as President Biden said, but so far, we haven’t seen it,” Sullivan said.

Sullivan added, “I don’t think it is in China’s interest to do this.”

His comments come after reports that the U.S. believes China is considering sending artillery and ammunition to Russia.

“I think it would alienate them from a number of countries in the world, including our European allies, and it would put them for square into the center of responsibility for the kinds of war crimes and bombardments of civilians and atrocities that the Russians are committing in Ukraine,” Sullivan said of China sending military aid to Russia, adding that “their weapons would in effect be used for the slaughter of people in Ukraine.”

“But that’s a decision Beijing is going to have to make for itself,” he added.

NBC News reported that intelligence suggests that China is considering sending artillery and ammunition to Russia, according to three current U.S. officials, one Western official and one former U.S. official briefed on the intelligence. These officials would not say what specific evidence they have to support their claims.

China’s Ministry of Foreign Affairs did not respond to NBC News’ earlier request for comment on the intelligence.

The Wall Street Journal was first to report details of what the U.S. believes Beijing is considering.

This is a developing story, please check back for updates.