US Secretary of State Antony Blinken said on Monday he had asked China's government to be vigilant about private companies that may be providing Russia with technology that could be used against Ukraine, although he said he had seen no evidence Beijing is providing lethal assistance to Moscow.

"What we do have ongoing concerns about, though, are Chinese firms, companies, that may be providing technology that Russia can use to advance its aggression in Ukraine and we have asked the Chinese government to be very vigilant about that," Blinken told reporters.

Blinken spoke on a rare visit to Beijing during which China and the United States agreed to stabilise their intense rivalry so it does not veer into conflict, although the visit did not yield any major breakthrough.

Blinken met with Chinese president Xi Jinping on Monday, the second day of his visit.

Western powers have provided Ukraine with billions of dollars in military assistance since Russia invaded in February 2022. China has faced accusations, which it denies, of supplying lethal weapons to Moscow. China and Russia announced a "no-limits" partnership shortly before Russia invaded Ukraine.

"With regard to lethal aid to Russia for use in Ukraine, we and other countries have received assurances from China that it is not and will not provide lethal assistance to Russia for use in Ukraine," Blinken said.

"We appreciate that, and we have not seen any evidence that contradicts that," he told reporters.

Asked for comment on Blinken's remarks, the Chinese embassy in Washington said China is committed to promoting peace talks and has not provided weapons to either side in the Russia-Ukraine conflict.

"We oppose the unfair prohibition or restriction on normal economic and trade activities between Chinese and foreign companies. We urge the US side not to undermine China's legitimate rights and interests in any form when handling the Ukraine issue and its relations with Russia," spokesperson Liu Pengyu said in an emailed statement.

- Reuters