Department, says a ship-based NMD system is technically possible.

CENTERFORSECURITYPOLICY: Freedom Flame 2013

While this is a significant sum, to be sure, if an apples- to-apples comparison were made, the price of purchasing and operating modern fighter aircraft wings or a class of surface ships or submarines would significantly exceed that associated with a ground-based NMD system.

CENTERFORSECURITYPOLICY: Sea-Based Missile Defenses -- for the Allies, for the U.S.

In stark contrast, the Conservatives support NMD and advocate its development as a pan-Nato defensive system.

BBC: National Missile Defence

France and Germany are also on the record as believing NMD could have grave implications for European defence - prompting fears of a split between Nato partners.

BBC: National Missile Defence

Minutes later, his official spokesman, Alastair Campbell, responded to a question from journalists saying that NMD was "a good idea" - though Downing Street insists that his remarks were taken out of context.

BBC: National Missile Defence

Colonel-General Leonid Ivashov, head of the Defence Ministry's international co-operation department, said the proposal would easily beat NMD, which Russia says could drain Europe financially.

CNN: UK signals support for missile plan