Moscow and Beijing have deepened ties amid Russia's military offensive on Ukraine, launched in February 2022.

"The most important issues will be discussed in a one-on-one meeting, the Ukrainian topic and Russian-US relations," Kremlin aide Yuri Ushakov told reporters.

Russia is rolling out the red carpet for Xi with a state visit, set to start on Wednesday, with the Chinese president also set to be guest of honour at Moscow's grand May 9 Victory Day parade on Red Square.

China has portrayed itself as a neutral party in the three-year conflict, although Western governments say its close ties to Russia have given Moscow crucial economic and diplomatic support.

Ukrainian President Volodymyr Zelensky in April accused China of supplying arms to Russia, and alleged Beijing knew of at least 155 Chinese nationals fighting alongside Russian forces.

Beijing denied that its citizens were being recruited en masse by Russia and urged Chinese nationals not to become involved in conflicts.