MADRID UN Secretary General Antonio Guterres said he sees no immediate possibility of reaching a comprehensive ceasefire in the war in Ukraine as both sides are convinced they can win, according to an interview published by Spanish newspaper El Pais on Tuesday.

Guterres, who is in Spain to receive the Charles V European Award, told El Pais the UN was instead focusing on talks with both Russia and Ukraine to solve concrete problems such as extending the Black Sea grain deal that is set to expire on May 18.

"Unfortunately, I believe that at this stage, a peace negotiation is not possible. Both sides are convinced that they can win," Guterres said.

"At the moment, I do not see any possibility of achieving immediately - we are not talking about the future - a comprehensive ceasefire, a peace negotiation," he added.

Russian forces launched a new attack on Ukraine on Tuesday as Russia celebrated the anniversary of the defeat of Nazi Germany in 1945, with Ukraine's air defences destroying 23 of 25 missiles fired, chiefly at the capital Kyiv, officials said.

The attack - the fifth in May - came a day after Russia launched its biggest drone swarm for months, striking Kyiv and the Black Sea city of Odesa and shelling other cities as Ukraine prepares for a major counter-offensive.

Asked about mediation efforts by China or Brazilian leader Lula, Guterres stressed that achieving peace in the conflict could not happen at the moment, though he hoped that "in the future it will".

He also praised Beijing's position on nuclear escalation being "unacceptable", describing it as "very important to avoid a temptation that would be an intolerable absurdity".

Nuclear tension has surged since Russia's invasion, as President Vladimir Putin has repeatedly warned that Moscow is ready to use its nuclear arsenal, if necessary, to defend its "territorial integrity".

(Reporting by David Latona; Editing by Philippa Fletcher)