The UK is hosting a closed meeting on Thursday of senior military leaders from the "coalition of the willing", as they draw up plans for a proposed peacekeeping force for Ukraine.

More than 20 countries are thought to be involved.

Prime Minister Sir Keir Starmer is expected to attend on Thursday afternoon after first visiting Barrow, where he is due to lay the keel of one of Britain's next generation of nuclear-armed submarines.

Plans for a Western-led peacekeeping force for Ukraine are said to be moving to an operational phase.

Senior military officers from nations that make up the "coalition of the willing", led by Britain and France, are due to discuss how this would work in practice when they gather at the UK's Permanent Joint Headquarters in Northwood.

Armed Forces minister Luke Pollard said they want the coalition to be a "credible force" that would allow Ukraine to "enjoy a lasting peace" and "reconstitute and rearm".

"[Vladimir] Putin won't stop if he wins in Ukraine. If he subjugates the entirety of Ukraine – which is his plan and has been for many years – he will simply rearm and look where else he can extend his influence and his domination," he told BBC Breakfast.

"That is not in our interest as a country, certainly not in the interest of our European friends."

Pollard said securing peace in Ukraine may mean "some boots on the ground", but the force will also "have a strong feature of air and maritime forces".

But there remain some major obstacles.

Russian President Vladimir Putin has said Moscow will not tolerate the presence of any Nato member troops in Ukraine, regardless of their role.

The US is also proving reluctant to provide the necessary air cover that prospective members say they need.

Sir Keir is expected to attend part of the meeting after first visiting Barrow where he will lay the keel of HMS Dreadnought, one of the next generation of nuclear-armed submarines.

On his visit to the town, Sir Keir will say Barrow is a "blueprint" for how defence spending can benefit a community.

He is due to announce that the King has agreed to grant Barrow the title of "Royal" in recognition of its contribution to national security.

Earlier he visited the crew of one of Britain's nuclear submarines, HMS Vanguard, as it returned to Scotland after patrolling the waters of the north Atlantic.

The prime minister told reporters the Kremlin respected the UK's nuclear arsenal because "we've got our own independent deterrent and we're committed to Nato".

"What is obviously important is they appreciate that it is what it is which is a credible capability," he said. "And that it most certainly is."

Defence Secretary John Healey, who joined the prime minister on the visit, stressed the government's "unshakeable" commitment to the UK's nuclear deterrent, which he called "the ultimate guarantor of our national security and the security of our Nato allies".