Washington: The United States is concerned about China's alignment with Russia amid the war in Ukraine and closely monitoring Beijing's activity to see if the country provides any military or sanctions evasion assistance to Moscow, a State Department spokesperson has said.

"Beijing claims to be neutral, but its behaviour makes clear it is still investing in close ties to Russia," the US spokesperson said on Friday in a statement to American broadcaster CNN.

On Friday, Russian President Vladimir Putin and Chinese President Xi Jinping discussed bilateral relations and regional problems via video link. During the call, Putin invited Xi to come to Moscow next year.

"The United States and Europe have warned the PRC (People's Republic of China) of the consequences of providing Russia military assistance for its war against Ukraine or systematic assistance with sanctions evasion," the spokesperson continued.

The State Department spokesperson said that the US is monitoring Beijing's activity closely and added that "those that side with Moscow in this unjust war will inevitably find themselves on the wrong side of history."

"The world is watching to see which nations stand up for the basic principles of freedom, self-determination, and sovereignty, and which stand by or tacitly support Russia in its premeditated and unprovoked war of choice," the spokesperson added.

This comes after the Chinese President told his Russian counterpart on Friday that both countries should strengthen their strategic coordination.

Xi stressed that both sides should make good use of existing mechanisms for further cooperation in economy, trade and energy, Xinhua news agency reported. The Chinese president said the world's second-largest economy is ready to resume normal cross-border travel with Russia and other countries in an orderly manner.

According to Xinhua, Putin said that in the current complex and severe international situation, Russia-China relations have maintained a sound momentum of development, witnessing steady cooperation progress in various fields, including energy, agriculture, and infrastructure.

The resilience, maturity and stability of Russia-China ties have been enhanced further, Putin said, adding that the significance of strategic coordination between the two countries has become more prominent.

Russia is willing to continue close coordination with China on multilateral platforms including the United Nations, the Shanghai Cooperation Organization, BRICS and the Group of 20, Putin said.

The Xi-Putin talks come as Russia on Thursday launched what Ukrainian officials described as one of the biggest missile barrages since the war began in February, CNN reported.

Ukrainian officials have been cautioning for days that Russia is preparing to launch an all-out assault on the power grid to close out 2022, the report added.