Britain, France and Ukraine earlier this week signed a declaration of intent that sets out deploying troops on Ukrainian territory after a ceasefire -- a plan which Moscow soundly rejected.

The "UK is now accelerating pound200 million to equip UK Armed Forces with new kit to be ready to deploy as part of the Multinational Force for Ukraine," the Ministry of Defence said in a statement.

That would include vehicle upgrades, communication systems and counter-drone protection.

"We are surging investment into our preparations following the Prime Minister's announcement this week, ensuring that Britain's Armed Forces are ready to deploy, and lead, the Multinational Force for Ukraine," Defence Secretary John Healey said while on a visit to Kyiv.

London has said its MPs will be able to debate and vote on the number of troops that would be sent if there is a ceasefire.

But Moscow rejected the post-war peacekeeping plan, saying such troops would be "considered legitimate military targets".

The announcement comes as UK media reported the Ministry of Defence was facing a pound28 billion shortfall over the next four years, despite government pledges to boost military spending amid rising tensions with Russia.

The Times newspaper first reported that the head of Britain's armed forces Richard Knighton warned Prime Minister Keir Starmer about the funding blackhole last month.

"We recognise demands on defence are rising, with growing Russian aggression, increasing operational requirements and preparations for a Ukraine deployment," Downing Street said on Friday, without directly addressing the reports.

The UK has committed to increase defence spending to 3.5 percent of GDP by 2035, in line with a NATO target.