US President Joe Biden laid out to his Chinese counterpart, Xi Jinping, the consequences Beijing will endure if it "materially supports" Russia's war effort in Ukraine, the White House said on Friday.

The executive mansion said Biden's two-hour secure video call with Xi "focused on Russia’s unprovoked invasion of Ukraine," with Biden outlining "our efforts to prevent and then respond to the invasion, including by imposing costs on Russia."

Biden "described the implications and consequences if China provides material support to Russia as it conducts brutal attacks against Ukrainian cities and civilians," the White House said in a statement.

"The President underscored his support for a diplomatic resolution to the crisis. The two leaders also agreed on the importance of maintaining open lines of communication, to manage the competition between our two countries," it added.

A senior administration official who briefed reporters on a conference call said Biden was "candid and direct," but declined to specify what ramifications he laid out for Xi.

"We will see what decisions China makes in the days and weeks ahead," the official said.

Russia's war against Ukraine started on Feb. 24. It has drawn international condemnation, led to financial restrictions on Moscow, and spurred an exodus of global firms from Russia.

At least 816 civilians have been killed and 1,333 injured in Ukraine since the beginning of the war, the UN said, while noting the true figure is likely significantly higher.

More than 3.27 million people have also fled to neighboring countries, according to the UN refugee agency. (Anadolu Agency)