LONDON, April 2, 1982 (UPI) -- Britain broke off diplomatic relations with Argentina Friday for seizing the Falkland Islands and warned that its naval forces racing to the area would defend the South Atlantic crown colony by force.
Defense Secretary John Nott said a ''substantial'' naval fleet was being readied to leave for the disputed island chain and join a naval force already in the South Atlantic.
The force being readied reportedly included six warships led by the aircraft carrier Invincible. Unconfirmed television reports said Royal Air Force transport planes had taken off from their base at Lyneham.
But Nott said Britain was still seeking a negotiated solution to the crisis that would avoid the use of force by Britain.
Prime Minister Margaret Thatcher held an urgent meeting with Royal Navy and Air Force chiefs of staff to review military preparations under way to take back the islands captured by an invasion force of 3,000 to 4,000 Argentine marines early Friday morning.
The Times said the Argentine invasion ''is as perfect an example of unprovoked aggression and military expansion as the world has seen since the end of Adolf Hitler'' and joined other newspapers in a call for Britain to retake the islands by force.
The Sun's banner headline said, ''It's War!'' and the Daily Express front page headline read ''Our Loyal Subjects, We Must Defend Them.''
The Daily Telegraph said the Thatcher government ''will have a lot of explaining to do'' over its handling of the crisis.
The spokesman for the opposition Labor Party said the Argentine government was a ''tinpot fascist junta'' which was pressing the Falklands issue to divert attention from soaring inflation.
Asked if the British government considered the invasion an act of war, Foreign Secretary Lord Carrington said, ''Under Article 51 of the United Nations charter any state which is the victim of armed attack has the right of self-defense. This clearly includes any action to repel or expel an invading force.''
Deputy Foreign Secretary Humphrey Atkins said Britain would ''sustain and defend the islands'' but he refused to comment on details of the force being dispatched to reclaim one of the last outposts of the British empire.
Nott said that because of poor communications he was unable to give any details on the takeover of the island, in which Argentine naval sources said one Argentine was killed and two wounded.
A force of 79 British marines are garrisoned on the island chain, populated by an estimated 1,900 English-speaking British subjects and reportedly rich in oil deposits.
Carrington announced Britain had broken off diplomatic relations with Argentina and ordered its diplomats out of the country within four days.
''Her Majesty's government,'' Carrington said, ''totally condemns this unprovoked military attack which was in total contravention to appeals made to both Britain and Argentina by the president of the U.N. Security Council.''
The cabinet met twice in emergency session and the government called an emergency session of parliament at 11 a.m. Saturday -- the first time the House of Commons has met on a Saturday since the Suez canal crisis 25 years ago. At the United Nations, British Ambassador Sir Anthony Parsons asked a special session of the Security Council to call for Argentina's withdrawal from the islands.
The Falklands, which lie 400 miles off the Argentine coast in the South Atlantic, were first settled by Britain in 1765, but they went through a period of Spanish and Argentine rule before they were recaptured by the British in 1832.
The two nations have held fruitless negotiations to resolve the status of the islands for the past 15 years. One possible reason for the bitter dispute is the reports of large petroleum deposits in the region.
In Washington, the State Department said it recognized Britain's claim to the islands and urged Argentina not to use force in the dispute.
Nott said the British government became aware of substantial Argentine naval exercises earlier this week, including amphibious maneuvers, and that a force was moving towards the Falklands.
Nott said that intensive diplomatic efforts were made to resolve the crisis and that Britain avoided military action until it became clear last night that Argentina was moving against the island.