WASHINGTON >> The U.S. and South Korea have called on China to use its influence over Russia and North Korea to prevent escalation after Pyongyang sent thousands of troops to Russia to aid Moscow’s war against Ukraine. Beijing has so far stayed quiet.

In a rare meeting earlier this week, three top U.S. diplomats met with China’s ambassador to the United States to emphasize U.S. concerns and urge China to use its sway with North Korea to try to curtail the cooperation, according to a State Department official, who spoke on condition of anonymity.

Secretary of State Antony Blinken said Thursday that the sides had “a robust conversation just this week” and that China knows U.S. expectations that “they’ll use the influence that they have to work to curb these activities.”

“But I think this is a demand signal that’s coming not just from us, but from countries around the world,” he said at a news conference in Washington with Defense Secretary Lloyd Austin and their South Korean counterparts. The U.S. says 8,000 North Korean soldiers are in Russia near Ukraine’s border and are preparing to help the Kremlin fight against Ukrainian troops in the coming days.

Beijing has forged a “no limits” partnership with Moscow, and while it has been a major ally for Pyongyang, experts say Beijing might not approve of the closer military partnership between Russia and North Korea because it sees it as destabilizing the region.

When asked about a meeting between U.S. and Chinese diplomats, Lin Jian, a spokesman for the Chinese foreign ministry, said at a briefing Wednesday in Beijing that he had “no information to provide.”

He added that China’s stances on Ukraine and on the Korean Peninsula have been consistent. China has called for a cease-fire and urged peace talks to end the war in Ukraine. And it has long advocated for a peaceful and stable Korean Peninsula.

The Russia-North Korea partnership runs contrary to Beijing’s goal for a peaceful Korean Peninsula, said Shi Yinhong, an international relations expert at China’s Renmin University. Beijing is “aware of the complexity and danger of the situation,” Shi said, noting the “fact that China hasn’t said anything yet on the military alliance agreement between North Korea and Russia indicates that China strongly disagrees with it.”