Keir Starmer’s “coalition of the willing” should enter Ukraine now to protect Europe’s security amid the US’s wavering support, an military expert has said.

The Times reported over the weekend that the prime minister is willing to deploy thousands of British troops to Ukraine for years to deter Vladimir Putin.

Defence chiefs from countries who have already signed up to the “coalition of the willing” will meet in London on Thursday to talk in detail about just what this commitment may entail.

It’s believed the alliance could send in as many as 30,000 troops, although it remains unclear whether they could fire at their Russian opponents amid fears that could trigger a new world war.

But Starmer has already stated that a British deployment would not happen without a security guarantee from the US – which Donald Trump has so far refused to give.

Senior consulting fellow with the Russia and Eurasia programme at Chatham House, Keir Giles, believes this is the wrong approach and Europe should act now.

In a policy brief for Estonia’s Baltic Defence College, Giles said: “European nations can, and should, and must, steadily and incrementally build their support to Ukraine by providing what they can as soon as they can, including the overt presence of European military forces inside Ukraine.”

Amid fears that Europe’s military is too weak to do this without the States, he said: “This could be a process of foreign assistance gradually replacing Ukrainian forces in functions and roles freeing them up to fight.

“At first, this would be very far from the frontline, but with the prospect of eventually relieving Ukrainian troops closer and closer to it.”

He added that any foreign troops deployed in Ukraine must operate under the assumption “that Russia will attack it, through ‘deniable’ or overt means” – and they must be willing and able to defend themselves.

Giles also dismissed the idea of calling this force “peacekeepers”, saying: “If a coalition of the willing arrives to support Ukraine, and its soldiers are killed by Russia without response in kind, this would in multiple ways be worse than not arriving in the first place.”

He said air protection would be key and must include a no-fly zone, even if its abilities are limited without US support.

The expert also pointed out that Nato “must remind Russia that even without the United States, Ukraine’s backers still include two nuclear powers”.

“It has to be made plain to Russia that this means any use of nuclear weapons in Europe at any scale will lead to a full-scale devastating response because that is the only option remaining. And that should be not a threat, but a promise of escalation,” he said.

Giles acknowledged that Europe is left “seeking the least worst of a number of very bad options”, and claimed the continent should have addressed the threat from Russia sooner.

But, he also questioned anyone who thinks Europe is “so atrophied by self-induced dependence on the United States” that it cannot support its own neighbourhood.

“There is a reasonable question from European taxpayers overall: what exactly are European armed forces for?” he said.

According to The Times, the UK, France, Turkey, Canada and Australia will be in talks to deploy troops to Ukraine this week, while others might assist with weapons and logistics.

Meanwhile, Trump has said he intends to call Putin on Tuesday to push for a 30-day ceasefire.