Russia has asked China for military equipment since its Feb. 24 invasion of Ukraine, the Financial Times and Washington Post reported on Sunday, citing US officials.
US National Security advisor Jake Sullivan will be in Rome on Monday to meet with China's top diplomat Yang Jiechi, the White House said earlier.
However, the spokesperson for China's embassy in Washington responded to media reports on Sunday that Moscow had asked Beijing for military equipment since launching its invasion of Ukraine by saying, "I've never heard of that."
The spokesperson, Liu Pengyu, said China's priority was to prevent the tense situation in Ukraine from getting out of control.
"The current situation in Ukraine is indeed disconcerting," he said in an emailed response to a query from Reuters.
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"The high priority now is to prevent the tense situation from escalating or even getting out of control."
Russia, which calls its action in Ukraine a "special operation," and China have tightened cooperation as they have come under strong Western pressure over human rights and a raft of other issues.
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Beijing has not condemned Russia's attack and does not call it an invasion, but has urged a negotiated solution.
The White House's National Security Council declined to comment.
The Washington Post said the unidentified US officials did not state the kind of weaponry that had been requested or how China had responded.
Sullivan will warn of the isolation China could face globally if it continued to support Russia, one US official said, without providing details.
Officials of the United States and other countries have sought to make clear to China in recent weeks that siding with Russia could carry consequences for trade flows, development of new technologies and could expose it to secondary sanctions.
Chinese companies which defy US restrictions on exports to Russia may be cut off from American equipment and software they need to make their products, US Commerce Secretary Gina Raimondo said last week.
It will be Sullivan's first known meeting with Yang since closed-door sessions in Zurich in October that sought to calm tension after an acrimonious public exchange between the two in Alaska a year ago.
China is the world's largest exporter, the European Union's largest trading partner, and the United States' top foreign supplier of goods, and any pressure on Chinese trade could have knock-on economic effects for the United States and its allies.
