Janet Yellen, US Secretary of the Treasury, has indicated that she had "difficult conversations" about Ukraine during her four-day visit to China.

As reported by Sky News, the US is concerned that Chinese companies are supporting Russia in its military invasion of Ukraine.

Yellen, who met with Chinese central bank governor Pan Gongsheng on Monday, warned that any banks facilitating the sale of military or dual-use goods to Russia could face US sanctions.

"I stressed that companies, including those in the PRC [People's Republic of China], must not provide material support for Russia's war and that they will face significant consequences if they do," she said.

When asked about the warning, Chinese Foreign Ministry spokesperson Mao Ning stressed that the US should "not smear or attack the normal state-to-state relations between China and Russia and should not harm the legitimate rights and interests of China and Chinese enterprises".

Media reports indicated that US Secretary of State Antony Blinken, in communications with his counterparts in the EU and NATO, stated that China is assisting Russia "at a concerning scale," providing tools and technology.

Officials recently told Politico that China is trying to convince Europe to allow Russia to sit at the table of future peace talks, possibly during a Peace Summit in Switzerland. Otherwise, Beijing threatens to boycott such meetings.

They said this message was reinforced during the European tour of Li Hui, China's Special Representative on Eurasian Affairs, in early March, where he discussed the future of Ukraine.