On the eve of a day of high diplomacy, with Nato, G7 and EU summits to discuss the crisis taking place in Brussels, Mr Stoltenberg again ruled out sending troops to Ukraine.

He said: “It is extremely important to provide support to Ukraine and we are stepping up. But at the same time it is also extremely important to prevent this conflict becoming a full-fledged war between Nato and Russia.”

President of Ukraine to attend summit virtually

Volodymyr Zelensky, the Ukrainian president, will address the summit by video link from Kyiv and is expected to renew his calls for a Nato-policed no-fly zone over his country.

That has been ruled out by leaders, including the US president, for fear of it leading to war with Russia. Nato members pledge to defend each other from attack but Ukraine is not a member of the alliance.

Mr Zelensky has signalled Kyiv could accept the end of its ambitions to join the alliance as part of a possible peace deal with Moscow.

Nato will also agree to “major increases” of forces “on land, in the air and at sea”  to bolster its eastern defences, Mr Stoltenberg said.

Four new battle groups will be deployed in Bulgaria, Hungary, Romania and Slovakia which would mean a total deterrent of eight multinational groups along the eastern flank, including existing troops in the Baltic nations and Poland.

Mr Stoltenberg accused China of giving political backing to Russia, warned Beijing against supplying Moscow’s war effort and told it to convince Mr Putin to stop the war.

He said: “I expect leaders will call on China to live up to its responsibilities as a member of the UN Security Council, refrain from supporting Russia’s war effort, and join the rest of the world in calling for an immediate, peaceful end to this war.”