The Army command announced today that its forces suffered a total of 1,366 casualties in the conflict with Britain over the Falkland Islands, including 261 dead and missing. The revelation added new force to a continuing national debate over the execution of Argentina's first modern war.

The new Army report brought estimates of Argentina's total casualty figure, including Air Force and Navy losses, to more than 1,700, among them at least 650 dead or missing.

The casualty figures for the 74-day conflict were released following demands by political leaders and media for an explanation by the armed forces of Argentina's losses. The Navy still has not released a full account of its losses, and there has been no official announcement on the number of planes and amount of arms that were destroyed or captured by Britain. The Air Force has acknowledged the loss of 54 men.

A group of Army staff generals presented the casualty report in a press conference this morning and heatedly defended the Army's role in planning and managing the failed occupation of the Falkands.

Disputing widespread accounts by returning soldiers and even some other armed forces commanders, the generals contended that Argentina's troops had been well supplied and well fed--until imposition of a blockade by the British--and that their arms were not greatly inferior to those of Britain.

The unusual press conference by half a dozen generals, including those in charge of Army supplies, arms, and logistics, reflected the continuing upheaval in both military and civilian circles here over the causes of Argentina's military and diplomatic failures following its April 2 invasion of the Falklands.

Much of the blame for the humiliating surrender by the invasion forces June 14 has fallen on the officials charged with the planning and strategy of the military defense of the Falklands. But the Army staff generals made clear today that they did not consider their operations responsible for the defeat and indicated that the search for culpability within the armed forces was far from over.

"To answer many of these questions, we must wait for the return of the officers in the operations zone," declared Gen. Gerardo Juan Nunez, brandishing one of the ration boxes he was in charge of sending to the Falklands. "They will have to deliver accounting, they will have to answer all of these questions."

British forces on the Falklands are still holding a number of Argentine soldiers and officers, including islands commander Gen. Mario Benjamin Menendez, while awaiting a signal from the military government that it will not continue hostilities in the South Atlantic. The Army report today said 335 of its personnel were being held by the British, in addition to Navy servicemen.

The report said 9,804 Army men had been sent to the Falklands, of whom 8,103 had now returned. A total of 156 were listed as dead, or presumed dead, while 105 were said to be missing and 883 were wounded. The report said 222 soldiers had become ill, and Army officials said 34 were treated for malnutrition during the nearly 11-week occupation.

Despite the number of soldiers listed as ill, the Army generals strongly denied widespread reports by returning conscripts that food was scarce in the last weeks of the conflict and that many soldiers suffered from frostbite or infected feet because of the soggy ground and lack of adequate equipment.

A major Argentine weekly magazine, Gente, devoted eight pages this week to interviews with dozens of veterans, many of whom complained about poor supplies and planning. "Why did we lose the war?" one soldier was quoted as saying. "Because we had to fight against two enemies: hunger and the English. Not only that, but the arms didn't work well."

The generals, frequently defensive as such charges were repeated by reporters, displayed Argentine-made rifles and special infrared scopes, read from advertisements in military magazines describing the quality of Argentine armaments, and invited reporters to test samples of soldiers' rations and winter coats.

In contrast to frequent assertions by Army officials after the surrender, Gen. Nelson Chillo said that Argentina's arms were adequate and that he had no firm reports about sophisticated weapons used by Britain and unavailable to Argentina.

Gen. Eduardo Esposito also told reporters that the British blockade of the islands was "total, a complete success."

The generals said that frequently after May 1, when British ships and planes began attacking airstrips on the Falklands as well as Argentine ships and planes, only one Argentine Hercules C130 plane would be able to reach the islands each day, carrying 14 tons of supplies. But the daily consumption of soldiers on the territory reached 30 tons of goods a day, they said.