US National Security Adviser Jake Sullivan, who is scheduled to meet with China’s top diplomat Yang Jiechi in Rome on Monday, has warned Beijing that it will “absolutely” face consequences if it assists Moscow in evading sweeping sanctions over the Ukraine conflict.

Following its February 24 invasion of Ukraine, Russia requested military equipment from China, raising concerns in the White House that Beijing may undermine Western efforts to assist Ukrainian forces in defending their country, according to several US officials.

Sullivan intends to express Washington’s concerns to Yang during their meeting, while also outlining the consequences and growing isolation China would face globally if it increased its support for Russia, according to a US official who declined to elaborate.

Asked about Russia’s request for military aid, first reported by the Financial Times, Liu Pengyu, spokesperson for China’s embassy in Washington, said: “I’ve never heard of that.”

He said China found the current situation in Ukraine “disconcerting” and added: “We support and encourage all efforts that are conducive to a peaceful settlement of the crisis.”

Liu said “utmost efforts should be made to support Russia and Ukraine in carrying forward negotiations despite the difficult situation to produce a peaceful outcome.”

Sullivan told CNN on Sunday that Washington believed China was aware Russia was planning some action in Ukraine before the invasion took place, although Beijing may not have understood the full extent of what was planned.

After the invasion began, Russia sought both military equipment and support from China, the U.S. officials said.

Sullivan told CNN Washington was watching closely to see to what extent Beijing provided economic or material support to Russia, and would impose consequences if that occurred.

“We are communicating directly, privately to Beijing, that there will absolutely be consequences for large-scale sanctions evasion efforts or support to Russia to backfill them,” Sullivan said. “We will not allow that to go forward and allow there to be a lifeline to Russia from these economic sanctions from any country, anywhere in the world.”

The meeting, planned for some time, is part of a broader effort by Washington and Beijing to maintain open channels of communication and manage competition between the world’s two largest economies, a senior Biden administration official said.

No specific outcomes were expected, the source added, speaking on condition of anonymity.

Chinese foreign ministry spokesman Zhao Lijian said the meeting’s focus was to “implement the important consensus” reached during the virtual meeting held between Chinese President Xi Jinping and U.S. President Joe Biden in November, which discussed “strategic stability” and arms control issues.

The two sides will exchange views on U.S.-China relations as well as international and regional issues of common concern, he said in a statement published on the ministry’s website.

Wang Huiyao, head of a Beijing think tank and adviser to the Chinese government, warned of “an escalatory spiral” in a column published in the New York Times on Sunday, and said China was “uniquely positioned to act as a neutral mediator between a Western-supported Ukraine and Russia” to end the war.

“Unpalatable as some in the West may find the idea, it is time to offer the Russian leader an off-ramp with China’s help,” Wang wrote.

U.S. officials were skeptical about the proposal given China’s ties to Russia and its spreading of misinformation related to the war.