Deputy Foreign Minister Wojciech Gerwel "expressed the hope that China... will condemn Russia's aggression, and exert pressure on Russia to return to compliance with the principles of international law," the Polish foreign ministry said.

China's special envoy visited the Polish capital after a two-day trip to Kyiv as part of a European tour to promote Beijing's plan to settle the Ukrainian conflict with Russia.

Beijing had announced Li would also travel to Russia, France and Germany.

The Polish foreign ministry added that Gerwel had condemned Russia's nuclear threats.

"Poland counts on concrete actions by China towards Russia -- the aggressor state blackmailing the world with the use of these weapons," it said.

The ministry added that "Poland notes with concern Beijing's declarations concerning its persistent will to strengthen its bilateral relations with Russia, the aggressor state."

Li told Ukrainian Foreign Minister Dmytro Kuleba and other officials this week that "there is no panacea to resolve the crisis".

Russia and China have close relations, with President Xi Jinping visiting Moscow in March and saying ties were "entering a new era".

And while China says it is a neutral party on the Ukraine war, it has been criticised for refusing to condemn Moscow for the invasion.