A deal struck between the UK and Ukraine will see warships and missiles sold to the country amid rising tensions with Russia

Defence Secretary Ben Wallace signed a treaty with Ukraine last week, under which the country’s government can access financing for contracts with UK suppliers to help beef up its naval capabilities.

It is expected to help deliver two mine counter-measures vessels (MCMV), the joint production of eight missile ships, the delivery of and retrofit of weapons systems to existing vessels, and the joint production of a frigate and consultancy and technical support for the building of naval infrastructure including the delivery of equipment.

It comes after Boris Johnson warned Vladimir Putin against making a “tragic mistake” as tensions rise on the border between Russia and Ukraine.

The Prime Minister, appearing at the Commons Liaison Committee, was asked about the problems between Belarus and Poland and the situation in Ukraine.

Thousands of migrants, mainly from the Middle East, have been amassing at the Belarus border with Poland for months.

Brussels has accused Belarus’s authoritarian president Alexander Lukashenko, a close ally of Russian President Vladimir Putin, of deliberately encouraging the migrants to breach its borders in retaliation for sanctions the EU has imposed in response to his repressive rule.

But reports on Wednesday suggested that hundreds had been moved to a nearby warehouse in Belarusian territory.

Downing Street has also voiced concern about the build-up of Russian forces on Russia’s border with Ukraine.

The Kremlin has dismissed claims that it is preparing to invade, after the Ukrainian defence ministry reported that around 90,000 Russian troops were massing in the area.

Mr Johnson said the two cases are “very different” because Poland has a Nato security guarantee, meaning that any action against it could trigger a response from the entire alliance.

Ukraine does not have the same guarantee from Nato, “so what we have got to do is make sure that everybody understands the cost of a miscalculation on the borders of both Ukraine and Poland would be enormous”.

“I think it would be a tragic, tragic mistake for the Kremlin to think there was anything to be gained,” Mr Johnson said.

A joint statement from Mr Wallace and Ukraine Defence Minister Oleksii Yuriyovych Reznikov said: “Ukraine and the United Kingdom are strategic partners in security and defence.

“Last week, an Intergovernmental Framework Agreement was signed in London.

“This document continues progress on joint projects to develop the capabilities of the Naval Forces of the Armed Forces of Ukraine, as agreed in June when the UK, Ukraine and industry signed a Memorandum of Implementation to collaborate to boost Ukraine’s naval capabilities.”

It said: “Our governments have no desire to be adversarial, or seek in any way to strategically encircle or undermine the Russian Federation. We are concerned by Russia’s military build-up and activity around the borders of Ukraine.

“Ukraine’s national sovereignty and territorial integrity is indisputable.

“The United Kingdom stands shoulder to shoulder with the people of Ukraine and will continue its long-standing determination to support them.

“We are unwavering in that support and together we remain vigilant and united in the defence of our common values and freedoms.”