It's a barely noticeable $250,000 item tucked away in the administration's fiscal 1980 proposal for $3 billion in foreign military aid. But that request -- to help train the Guatemalan armed forces -- seems certain to trigger controversy when Congress turns its attention to the foreign aid bill.

The problem arises not from the size of the amount but from its symbolism. In proposing to provide even minimal help to the Guatemalan military, the administration is exposing itself to questions from liberal members of Congress about whether it is retreating from President Carter's much-discussed championing of human rights.

Two years ago Guatemala was one of six Latin American countries -- the others are Brazil, Argentina, Chile, Uruguay and El Salvador -- that angrily rejected U.S. military assistance on the grounds that Washington's pressures over human rights questions were an interference in their internal affairs.

Guatemala has now become the first of the six with which Washington hopes to reestablish its old military ties. Yet, it is taking this step at a time when U.S. and Latin American rights activists continue to charge Guatemala with such abuses as torture by its security forces and terrorism by rightists groups covertly allied with the military.

In addition, Guatemala periodically has continued to threaten the use of military force to assert its territorial claims against neighboring Belize. And, within the context of Central American politics, it has identified itself increasingly with Nicaraguan President Anastasio Somoza -- a man Washington has been unsuccessfully pressuring to step aside in hopes of ending Nicaragua's bloody internal turmoil.

The parallels with Nicaragua are expected to be a big factor in the upcoming debate over renewed military aid to Guatemala. Despite Washington's current estrangement from Somoza, U.S. human rights groups and Latin American democratic governments have not forgotten the long period when the United States was the chief supplier and mentor of Somoza's armed forces.

In the view of the rights advocates, the lesson of Nicaragua demonstrates the folly of a close U.S. identification with Central America's military regimes. Guatemala, while nominally a democracy, is controlled from behind the scenes by the armed forces. Its current president. Gen. Romeo Lucas, was the candidate of the military when elected last year.

Although administration officials seek to downplay the differences, these factors are known to have caused a sharp dispute within the State Department over the wisdom of reinstating military aid to Guatemala. Department over the wisdom Department sources acknowledge privately that the decision was opposed by the bureau of human rights, which has responsibility for raising questions of rights abuses when a country is under considration for military or economic aid.

According to the sources, though, the decision to go ahead was due primarily to the strong advocacy of Viron P. Vaky, assistant secretary of state for inter-American affairs. His position raised quite a few eyebrows within the department.

Vaky's predecessor, Terence A. Todman, had come under heavy fire from liberal circles for allegedly not showing sufficient concern about human rights. When Vaky succeeded Todman last summer, administration officials sought to leave the impression he would take a stronger line on rights abuses.

Some department sources insist, however, that the pressures exerted by Vaky on behalf of Guatemala should not be seen as a sign of further U.S. deemphasis of Carter's human rights policy. These sources note that, in all military aid decisions, other factors -- such as U.S. security and economic interests -- are considered and these played a role in the Guatemala case.

Specifically, the sources said, Vaky and other department specialists in Latin America were concerned that U.S. relations with the Guatemalan military were deterioration to the point of endangering all of Washington's influence in the largest and most populous Central American country.

As a result, the sources said, when Guatemala requested some resumption of military assistance, the move was viewed as a chance to use a modest program -- principally enabling Guatemalan officers and military technicians to gain advanced training in the United States -- as a wedge to get back on better terms with the military leaders.

In addition, the sources said, at the time the matter was under debate last summer and fall, there were signs of an improving human rights situation within Guatemala. The government there was cooperating with the United States in an unsuccessful attempt to mediate the conflict between Somoza and his opponents in Nicaragua.

Some sources even contended that the request to renew military training assistance was a reward for Guatemala's participation in the Nicaragua mediation.

In the months since the decision was made, though, there have been signs of a new upsurge of rightist-inspired murders in Guatemala. These were climaxed by the murder, in late January, of former foreign minister Alberto Fuentes Mohr, a prominent political moderate, and subsequent charges that the Guatemalan government has not pressed very hard to find his killers.

As a result, when the Guatemala request comes up before Congress it seems certain to spark heavy liberal opposition and a debate about whether the Carter administration, despite its much-publicized rights policy, is setting a precedent that would move the United States back into its old, cozy relationships with the Latin military.