Britain is sending long-range Storm Shadow missiles to Ukraine, Defence Secretary Ben Wallace said on Thursday.
Announcing the decision in the House of Commons, Mr Wallace said the weapons would give Ukrainians “the best chance to defend themselves” against the Russian invasion.
The air-launched cruise missiles developed in the UK and France have a range of about 560km and deliver a conventional warhead weighing 450kg to its target.
The Shadow missiles, which weigh 1,300kg, have the ability to clear soil or enter a bunker before a controlled detonation of the warhead is triggered.
“Storm Shadow is a long-range, conventional-only, precision strike capability,” Mr Wallace said.
“It complements the long-range systems already gifted [by the UK] including Himars and Harpoon missiles, as well as Ukraine's own Neptune cruise missile and longer-range munitions elsewhere gifted.
“The donation of these weapons systems gives Ukrainians the best chance to defend themselves.”
In a speech in the House of Commons, the minister said at least 23,000 Ukrainians have been killed or wounded since Russia launched its full-scale invasion in February 2022.
He said that, during several trips to the Eastern European nation in recent months, he has seen destroyed buildings and infrastructure, which he called “visible and tragic symbols of the Kremlin’s desperation”.
Mr Wallace said that, more than a year into the war, Russia “can only occupy the rubble left by their destruction”.
He dismissed Moscow’s Victory Day Parade earlier this week, saying “all it did was showcase this historic failure” in Ukraine.
Dmitry Peskov, Russian President Vladimir Putin’s spokesman, called the delivery of the jets “extremely negative”.
“This will demand an adequate response from our military, which will, naturally, from a military point of view, find corresponding solutions,” Mr Peskov said.
Earlier, reports suggested the Storm Shadow missiles had already reached Ukraine.
Alicia Kearns, chairwoman of the House of Commons' foreign affairs committee, wrote on Twitter: “If true, this is good news. We must do everything we can to even the odds for our Ukrainian allies. Defence is never an escalation.”
Lt Gen Ben Hodges, a former commander of US forces in Europe, welcomed Britain's donation.
“Well done UK!” he wrote on Twitter. “This will give Ukraine capability to make Crimea untenable for Russian forces.
“Commander, Black Sea fleet is now faced with the destruction of ships, facilities in Sevastopol or repositioning ships to Novorossiysk, a much less capable port for support of the Fleet.”