Russian leader Vladimir Putin said President Xi Jinping will visit Russia and that relations between Moscow and Beijing had reached "new frontiers" amid US concerns that Beijing could provide material support to Russia's invasion of Ukraine.

Chinese weapons supplies to Russia would threaten a potential escalation of the Ukraine war into a confrontation between Russia and China on the one side and Ukraine and the US-led NATO military alliance on the other.

Putin welcomed China's top diplomat, Wang Yi, to the Kremlin, telling him that bilateral trade was better than expected.

He added: "We await a visit of the president of the People's Republic of China to Russia, we have agreed on this.

"Everything is progressing, developing. We are reaching new frontiers."

China is also trying to appear as a mediator and is expected to reveal its own "political solution" to the Ukraine conflict this week while still maintaining close ties with its ally Russia.

"With the Russian side, we are ready to strengthen our strategic partnership and our in-depth cooperation," Wang told Putin.

Wang insisted the partnership between the two countries was "not directed against any third country and does not give in to pressure."

Earlier Wang met with his Russian counterpart Sergei Lavrov. "Despite the high turbulence on the world stage, we are demonstrating our solidarity and readiness to defend each other's interests based on the respect for international law and the central role of the United Nations," Lavrov said.

Wang is on the last stop of a European tour during which he met with Ukrainian foreign minister Dmytro Kuleba.

AGENCE FRANCE-PRESSE, REUTERS

Wang Yi and Vladimir Putin meet in Moscow. reuters

Xi preparing to visit Moscow, says Putin