NATO's chief said Wednesday that the military alliance has seen “some signs” that China may be planning to support Russia in its war in Ukraine, and strongly urged Beijing to desist from what would be a violation of international law.

NATO Secretary General Jens Stoltenberg also told The Associated Press in an interview that the alliance, while not a party to the war, will support Ukraine “for as long as it takes.”

Asked whether NATO has any indication that China might be ready to provide arms or other support to Russia’s war, Stoltenberg said:

“We have seen some signs that they may be planning for that and of course NATO allies, the United States, have been warning against it because this is something that should not happen. China should not support Russia’s illegal war.”

Stoltenberg said potential Chinese assistance would amount to providing “(direct) support to a blatant violation of international law, and of course (as) a member of the U.N. security council China should not in any way support violation of the U.N. charter, or international law.”

On Wednesday, Russian President Vladimir Putin hosted the Chinese Communist Party's most senior foreign policy official — Wang Yi — raising concern in the West that Beijing might be ready to offer Moscow stronger support in the almost year-old war.

China has pointedly refused to criticize the invasion of Ukraine while echoing Moscow’s claim that the U.S. and NATO were to blame for provoking the Kremlin. China, Russia and South Africa are holding naval drills in the Indian Ocean this week.

U.S. Secretary of State Antony Blinken has said any Chinese involvement in the Kremlin’s war effort would be a “serious problem.” Ties between China and the U.S. are under severe strain over Taiwan and other issues.

Stoltenberg spoke to The Associated Press in Warsaw, following a meeting of NATO's nine eastern flank members with U.S. President Joe Biden on the region's security.

He stressed that while NATO “is no party” to the Ukraine conflict its tasks are to “ensure that Ukraine prevails” and to “prevent this war from escalating beyond Ukraine and becoming a full-fledged war between Russia and NATO.”

He said the main message from the meeting in Warsaw was that “we will provide support to Ukraine for as long as it takes.”

It would be a "tragedy for the Ukrainians if President Putin wins in Ukraine,” Stoltenberg said, and also “dangerous for all of us” because it would “send the message to all authoritarian leaders that when they use military force, they get what they want.”