Argentina's military, despite misgivings about President Leopoldo Galtieri's management of the Falkland Islands crisis, is now locked into a unified stance behind the general's apparent determination to battle a British task force rather than yield sovereignty, according to informed sources here.

While some Army and Air Force commanders are reported to be deeply concerned about the possible consequences of a military conflict in the South Atlantic, the nearness of the British fleet to the islands and the lack of a broad civilian movement urging moderation have prevented any conciliatory sentiment from emerging openly within the military command, military sources say.

At the same time, the hard-line position of high Navy commanders and Galtieri's dramatic statements that the South Atlantic islands belong to Argentina have made it impossible for the military president to back down without serious loss of prestige.

As a result, Argentine military analysts say the military would have to suffer a reverse in an armed conflict with Britain before a shift in position on the crucial issue of Argentine sovereignty over the islands could be embraced.

These analysts say the unwieldy and inflexible nature of the military power structure here means that only a clear failure by the ruling junta of service chiefs could prompt a coalition of Army and civilian leaders to force a major shift in position. Such a move would be likely to prompt a government crisis in which the power of all three junta members would be at stake.

"The construction of the military government under Galtieri eliminates the possibility of a moderate change," said one informed Argentine military analyst. "If there is a failure, it will mean the downfall of the entire junta, and there is no process for handling such a situation."

The rigidity of the command arises from the roots of political authority under the military government and the unusual way in which the islands were seized, analysts and military sources said.

Although the position of Galtieri as president and Army commander-in-chief is at stake, he has had to respond to only a small circle of associates in managing the defense of the islands and determining Argentina's negotiating position.

Retired general Roberto Viola, the previous military president, directed government policy but had to respond to--and was eventually removed by--the three-man junta because he was no longer commander of the preeminently powerful Army.

Galtieri, however, remained Army commander-in-chief after taking over as president last December. As a result, the aggressive, 55-year-old general is the most influential member of the only body empowered to review his actions as president.

The major strategic decisions in the crisis, including the original order for the April 2 invasion, were approved jointly by the junta. As a result, the junta is commonly bound to defend Argentina's sovereignty claim, analysts here say.

During the past three weeks, subtle differences have emerged among the three armed forces leaders, these analysts and sources note.

Adm. Jorge Anaya, whose service had the primary role in an invasion it had been planning for years, is reported to have been resistant to concessions already made by Argentina and to acceptance of Secretary of State Alexander M. Haig Jr. as a neutral third party.

The Navy's relative hostility to the U.S. role is consistent with reservations in its ranks long before the crisis over Galtieri's policy of strengthening the strategic alliance between Argentina and the United States, say sources linked to the Navy.

The Air Force commander, Gen. Basilio Lami Dozo, has offered some of the most moderate formulations of the negotiations in public, and some Air Force commanders are reported by military analysts here to be uneasy with their potentially crucial defensive role in a confrontation that was initiated with little Air Force involvement.

Yet, sources here stressed that there is little likelihood of an open split between Galtieri and the other junta members that would lead to a shift of power or of negotiating stance. "All three of them signed the invasion order," said one analyst. "They are all committed to the success or failure of this."

The junta's only political vulnerability, say analysts here, lies in the possibility of a perception by the second rank of military commanders--particularly in the Army--of a failure or backing down on the Falklands dispute.

Although the 10 of Argentina's 55 active Army generals who hold the title of division commander are the key to Galtieri's internal support, few--maybe none--were consulted in advance about the invasion, according to an Army source.

Now, the source said, some Army elements believe Galtieri and the military junta placed themselves in a dangerously inflexible position through initial miscalculations.

"This was planned to begin and end as a naval operation," the source said. "No one imagined the situation that has developed."

The small command that planned the invasion apparently did not anticipate that Britain might respond with a major military operation. Nor did they foresee the possible consequences of a South Atlantic battle with Britain--such as a crippling of Argentina's fleet, international diplomatic isolation and long-term damage to an already stricken economy.

Some military leaders say Galtieri's government may have moved too quickly to proclaim unnegotiable control over the islands after the invasion. This stand, which leaves little room for Argentine movement on the root issue of the dispute with Britain, cannot now be changed without a loss of face for the junta.

At the same time, the junta's inability to retreat from its aggressively advanced position may force Argentina into a fight that would mean an equally great failure. Such a loss of prestige--through either surrender or defeat--could empower otherwise subordinate officers to move against Galtieri.

"The lines of command are very powerful," said one high officer who now is retired. "You don't question openly your commanding officer unless the authority is somehow stripped away."

Thus, say analysts, just as Galtieri and the other junta members cannot back away from their assertion of sovereignty over the Falklands without risking their power, so the military commanders below the junta are unlikely to pressure their superiors until their policy has manifestly failed.

The only force that could otherwise provoke a conciliatory movement in the armed forces would be strong opposition to the government's position by civilian political and labor leaders, analysts here say, but many of these leaders continue to endorse publicly a hard-line negotiating stance.

In addition, one military analyst said, the British fleet is now too close to Argentine positions on South Georgia for any moderate movement in the military to be acceptable. "With the fleet that close, anybody who tries to be conciliatory is going to be called a traitor," he said. "No one can look like they are trying to avoid a fight."