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Armed Forces Minister James Heappey said Britain would provide Ukraine with the 1.8 metre, 50 kilogram air-launched missiles “in the next few weeks”.
The UK said it wants the war in Ukraine to lead to changes in global security arrangements.
On Wednesday, Prime Minister Boris Johnson dismissed fears there could be nuclear reprisals from Russia if its army becomes bogged down in Ukraine, while the Nato military alliance said it hoped Ukrainian heavy artillery will frustrate Russian attacks.
Brimstone missiles have been used by British air power in Libya and Syria. They have a longer range than some of the systems friendly nations have supplied to Ukraine since the Russian invasion at the end of February.
Manufacturer MBDA said they can be used against fast-moving land and sea targets. In Ukraine, the missiles would be fired from land against targets at sea.
“Recently Ukraine has been asking for longer-range ground attack missiles, and the government has been exploring if stocks of Brimstone could be released for such purposes,” Mr Heappey said.
“This remains very much in line with our principle of evolving our support to Ukraine as the conflict evolves and their capability requirements change.”
Defence Secretary Ben Wallace told the House of Commons that Brimstone missiles were on Ukraine’s shopping list before the war began.
“On Brimstone missiles, we made a commitment I think nearly 18 months ago, two years ago, when we were selling fast attack patrol boats to Ukraine, that we would sell [them] armed with maritime Brimstone missiles.
“We would do that. They are not at present in the country. Those ships have not been yet purchased or delivered.
“However, if we wish to provide Brimstones in whatever guises they are, I will inform members of this House when we do it. I don't close it off as an opportunity. I think it's a perfectly legitimate thing.”
“First and foremost, we will look to provide if we do, Brimstone for the land, using stock we already hold but not as yet on the sea,” Mr Wallace said.