The country will purchase 12 nuclear weapon-capable F-35A fighters, expanding the country's deterrence arsenal, which is currently limited to submarine-launched missiles.

"These F35 dual capable aircraft will herald a new era for our world-leading Royal Air Force and deter hostile threats that threaten the UK and our Allies," Starmer said in a statement on Tuesday.

NATO Secretary General Mark Rutte was quoted in the statement as saying: "I strongly welcome today's announcement," calling it "yet another robust British contribution to NATO".

Downing Street described it as the "biggest strengthening of the UK's nuclear posture in a generation", adding that Starmer would announce the plan at summit on Wednesday.

Since the end of the Cold War, British nuclear deterrence within the Atlantic alliance was provided solely by missiles aboard Royal Navy submarines.

Heloise Fayet, a nuclear specialist at the French Institute of International Relations (Ifri), told AFP the announcement illustrates "the continued re-nuclearization of Europe, the renewed need for nuclear weapons, and the strengthening of NATO's deterrence, in the face of an adversary, Russia".

The F-35A, manufactured by US company Lockheed Martin, is a variant of the F-35B already used by the United Kingdom, but which can carry nuclear warheads in addition to conventional weapons.

The acquisition has been a long-standing request from the Royal Air Force.

The planes are expected to be stationed at Marham Air Force Base in eastern England.

- 'New risks'-

Leaders from NATO countries are gathering in The Hague this week where they are expected to pledge that they will spend five percent of GDP on defence by 2035, under pressure from US President Donald Trump.

The UK had already committed on Monday that it would meet the spending target.

London said in February that it would hike its defence budget to 2.5 percent of GDP by 2027 and three percent after 2029.

British Defence Secretary John Healey warned on Tuesday that the UK faced "new nuclear risks, with other states increasing, modernising and diversifying their nuclear arsenals".

Seven NATO members, including the US, Germany and Italy, currently have dual-capable aircraft stored on European soil that can carry American B61 nuclear warheads -- the same type that Britain is expected to use.

In June, Britain announced that it would build up to 12 new attack submarines and six munitions factories as part of efforts to re-arm the country in the face of "threats", particularly from Russia.

The dozen nuclear-powered subs will be equipped with conventional weapons and form part of the AUKUS military alliance between the UK, the US and Australia.

Starmer also confirmed that London would spend pound15 billion ($20.4 billion) on its nuclear warhead programme.

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