LONDON (AP) _ Britain's defense minister said Tuesday that it may be ``some months'' before the Royal Navy's nuclear-powered hunter-killer submarines are back in service.

One of the 12 submarines, the HMS Tireless, has been under repair in Gibraltar after a defect caused minor leaking. The whole fleet was subsequently recalled for maintenance checks.

Defense Minister John Spellar told the House of Commons that the flaw was located in the pipes that form part of the reactor cooling system, and that he feared it might be ``generic.''

``Initial indications are that the defect may have arisen from the original construction of the submarine and that it is present in other submarines, albeit at an early stage,'' he said. ``It may take some months for submarines to be repaired where this is necessary.''

Spellar said correcting the problem would ``clearly have an impact on our operational program,'' but added that every effort would be made to mitigate that by using other assets.

The submarines are a vital part of the Royal Navy's operational capability and are often used to protect larger submarines armed with the Trident nuclear deterrent.

Spellar stressed that the Vanguard class Trident submarines, which are of a different design, were not affected.

The HMS Tireless was between Sicily and North Africa when the leak was discovered May 12.