Biden adviser to meet top China diplomat in Rome over Russia relationship

The White House national security council declined to comment, however, on reports that Russia has asked China for military equipment since its invasion of Ukraine on 24 February.

The Financial Times, Washington Post and New York Times reported the request on Sunday, citing US officials.

The Washington Post said the unidentified US officials did not state the kind of weaponry that Russia requested or how China responded.

Earlier, Sullivan told CNN the US believed China was aware Russia was planning action in Ukraine before the invasion took place, though Beijing may not have understood the full extent of what was planned.

Now, Sullivan said, Washington was watching closely to see to what extent Beijing provided economic or material support to Russia, and would impose consequences if it did.

No specific outcomes were expected from the Rome meeting, the source said, speaking on condition of anonymity.

The US on Saturday said it would rush up to $200m of additional weapons to Ukrainian forces as they try to defend against Russian shelling in the largest conflict in Europe since the second world war.

The Russian assault has trapped thousands of civilians in besieged cities and sent 2.5 million Ukrainians fleeing to neighboring countries.

The US and its allies have imposed unprecedented sanctions and banned Russian energy imports, while providing billions of dollars of military and humanitarian aid to Ukraine.

Individually and together they have appealed to China, Gulf nations and others that have failed to condemn the invasion to join in isolating Russia.