NATO Secretary-General Mark Rutte has warned that a Russian victory over Ukraine would undermine the dissuasive force of the world’s biggest military alliance and could cost trillions of dollars to restore the organization's credibility.

DAVOS (Reuters) - NATO Secretary General Mark Rutte reaffirmed on Thursday the need to step up support for Ukraine, adding it was vital Russia did not win as it could result in Russian President Vladimir Putin 'high fiving' the leaders of North Korea and China.

Any attempt to get Ukraine into Nato will run into a “buzz saw” in Washington unless Europe pays for it, a top diplomat for Donald Trump has said.

Putin has said repeatedly that he is prepared to negotiate an end to the war, which first began in 2014, but that Ukraine would have to accept the reality of Russian territorial gains, which are currently about 20% of its land. He also refuses to accept Ukraine joining Nato, the military alliance of Western countries.