Washington: US President Joe Biden spoke with Chinese President Xi Jinping over a secured video call on Friday in the backdrop of the Russia-Ukraine conflict.

China's response to Russia's invasion of Ukraine has already troubled western observers. White House officials are watching with growing concern the budding partnership between Xi and Russian President Vladimir Putin.

Biden, on Thursday, said that the Chinese counterpart "does not believe democracies can be sustained in the 21st century." According to CNN News, Secretary of State Antony Blinken on Thursday said, "We're (US) concerned that they're (China) considering directly assisting Russia with military equipment to use in Ukraine."

United Nations has "deep concerns" on China's alignment with Russia at present time, a US official said, adding that the national security adviser was directed about those concerns and the potential implications and consequences of certain actions.

"We do have deep concerns about China's alignment with Russia at this time, and the national security adviser was direct about those concerns and the potential implications and consequences of certain actions," the official said.

White House press secretary Jen Psaki underscored that message, suggesting the US would take action against China should it help Russia.

"We've been clear there would be consequences," she said at a White House briefing.

US National Security Advisor Jake Sullivan met Chinese Communist Party Political Bureau Member and Director of the Office of the Foreign Affairs Commission Yang Jiechi and raised a range of issues in US-China ties, with "substantial discussion" of Russia's war against Ukraine.

"Sullivan raised a range of issues in US-China relations, with substantial discussion of Russia's war against Ukraine. They also underscored the importance of maintaining open lines of communication between the United States and China," a White House readout said. The meeting between the US and Chinese diplomates was held in Rome, Italy.

"Their meeting followed up on the November 15, 2022, virtual meeting between President Biden and President Xi," the readout said.

Earlier, the US had warned China of the consequences of helping Russia bypass sanctions.

On February 24, Russia began a special military operation in Ukraine after the Donetsk and Luhansk people's republics requested help in defending themselves.

The Russian Defence Ministry said the special operation is targeting Ukrainian military infrastructure only and the civilian population is not in danger.

The West however denies these claims by the Russians and in response, Western nations have imposed comprehensive sanctions on Moscow. In addition, they introduced sanctions on Belarus for supporting Russia's operation in Ukraine.