"Here in China everyone knows that an escalation (of the war in Ukraine) would have consequences for us all," Scholz told reporters.

"That is why it is very important for me to stress that everyone says clearly that an escalation via the use of a tactical nuclear weapon is ruled out," he added.

"I am pleased that we at least reached agreement on that."

Scholz said after talks with Chinese President Xi Jinping that he had insisted "the Russia war in Ukraine is a dangerous situation for the whole world".

He told Xi earlier that "it is important for China to use its influence on Russia".

"Russia must immediately stop the attacks under which the civilian population is suffering daily and withdraw from Ukraine," Scholz said.

The White House said this week that repeated discussion by Russian officials of the potential use of nuclear weapons in Ukraine has left Washington worried it could become a reality.

"We have grown increasingly concerned about the potential as these months have gone on," said White House national security spokesman John Kirby.

Russia's foreign ministry responded that the world's "top priority" should be to avoid a clash of nuclear powers "in the current difficult and turbulent situation".