Ronald Reagan made secret plans to loan Britain a U.S. warship if she lost an aircraft carrier during the Falklands War, it has emerged.
The then-president was prepared to support Prime Minister Margaret Thatcher despite the U.S. being officially neutral during the 1982 conflict.
The stunning revelation was made by John Lehman, the former U.S. Secretary of the Navy, to the U.S. Naval Institute on Tuesday.
Mr Reagan would have loaned Britain the use of the amphibious warship USS Iwo Jima should harm have come to either HMS Invincible or HMS Hermes, which the Royal Navy had deployed to defend the islands from Argentinian forces.
Close ties: Ronald Reagan made secret plans to loan Margaret Thatcher a U.S. warship if Britain lost an aircraft carrier during the Falklands War, it has emerged
Loan: Mr Reagan would have handed Britain the use of the amphibious warship USS Iwo Jima (pictured) should harm have come to either HMS Invincible or HMS Hermes, which the Royal Navy had deployed to the Falklands
Mr Lehman said that he formulated the plans to stand behind Mrs Thatcher with Secretary of Defence Caspar Weinberger following a British request.
Mr Reagan is said to have approved their proposal without hesitation, telling Mr Lehman: 'Give Maggie everything she needs to get on with it.'
The plans were put together in complete secrecy.
Mr Lehman said: 'We would leave the State Department, except for [Secretary of State Al] Haig, out of it.
'As in most of the requests from the Brits at the time, it was an informal request on a "what if" basis, Navy to Navy.'
Both HMS Invincible or HMS Hermes were equipped to handle five vertical take-off Sea Harriers armed with American Sidewinder missiles.
HMS Invincible was one of two aircraft carriers deployed to defend the Falklands from Argentinian forces. She was decommissioned in 2005
Royal Marines take part in an exercise aboard HMS Hermes during the Falklands conflict
These specifications made the USS Iwo Jima an ideal replacement as, although primarily a helicopter carrier, it was able to operate the U.S. version of the Sea Harrier.
It is likely that the ship would have been manned by a mix of retired seamen and privately contracted Americans familiar with the ship's operating systems.
Admiral James 'Ace' Lyson, commander of the U.S. Second Fleet in 1982, helped plan the possible deployment of a U.S. ship in the South Atlantic.
Now retired, he said: 'We decided that the USS Iwo Jima would be the ship that would be the easiest for the British to operate and would make for a smooth transfer.
'We also identified "contract advisors" who would be on board to help the British with some of the systems.'
The revelation comes as diplomatic relations between Britain and Argentina reach their lowest point since the war.
Falkland residents have announced plans for a referendum next year in an attempt to fend off Argentinian claims to the territory, which have become more vocal around the 30th anniversary of the conflict.
Last week, David Cameron was involved in an extraordinary stand-up row with Argentina’s president Cristina Fernandez de Kirchner over the future of the Falkands.
The South American leader appeared to attempt to thrust a package stuffed with documents about her country’s claim to the British territory into Mr Cameron’s hands at the G20 summit in Mexico.
To her fury, the Prime Minister refused to accept it – and insisted that she respect the views of the islanders, who want to remain British.