Beijing has so far abstained from condemning Moscow's assault on its pro-Western neighbour as an "invasion" as it seeks to maintain close ties with Russia.

But Foreign Minister Wang Yi on Tuesday said China "deeply regrets that conflict has broken out between Ukraine and Russia, and is paying extreme attention to the harm suffered by civilians", state broadcaster CCTV reported.

"There is no alternative... It must be China, I am sure of that," Borrell said in an interview with Spanish daily El Mundo published on Friday evening.

"Diplomacy cannot only be European or American. Chinese diplomacy has a role to play here," he added.

"We have not asked for it and neither have they (China), but since it has to be a power and neither the US nor Europe can be (mediators), China could be."

Borrell said it was "obvious" that the EU and the United States could not mediate and ruled out reviving the so-called Normandy format, a four-way diplomatic framework involving Russia, Ukraine, France and Germany.

The format was established in 2014 in a bid to end fighting between Ukraine and Russian-backed separatists in the east of the country.

Talks between Moscow and Kyiv to seek a way to end the bloody conflict will resume on Monday, Ukrainian negotiator David Arakhamia said Saturday, as Russian President Vladimir Putin's invasion entered its 10th day.