Guatemala's new ruling military junta today came under pressure from young military officers and civilian politicians to set a date for a free democratic election to choose a civilian government within six months.

Demands that the three-man junta declare its rule "temporary" came as the junta issued its first governmental decree, officially annulling the March 7 national elections on the ground of fraud without mentioning any intention of holding the new elections that were the prime objective of the young officers' movement that brought the junta to power Tuesday.

Gen. Efrain Rios Montt, the junta president, sought, meanwhile, to consolidate his power by reshuffling Army commands, swearing in new Cabinet ministers and replacing the 27-year-old infantry lieutenant who had taken over the national police force directorship Tuesday with a loyal colonel who shares his own traditional beliefs in the system of military hierarchy.

Just how free Rios Montt is to act remained a subject of speculation two days after the coup as his every move, and meeting, in this capital's ornate presidential palace was dogged by the armed lieutenants, captains, majors and colonels who had been instrumental in toppling Gen. Romeo Lucas Garcia and his handpicked successor, Gen. Angel Anibal Guevara.

The young officers, six of whom have been named special "advisers" to the junta, remained a constant armed presence within the presidential palace.

During the day, Gen. Rios Montt flew to garrisons to meet with commanders and a large number of junior officers sympathetic to the coup. At the military installations, according to informed sources, Rios Montt stressed the need to restore Army discipline and its chain of command, while the young officers argued for the elections that they hoped could cleanse Guatemala's international image.

Sources close to the yuoung officers said they had staged their coup in the hope of "wiping clean" the Guatemalan political slate, so that their nation, and Army, could receive renewed U.S. economic and military aid that had been suspended on human rights violations grounds early on in Lucas Garcia's presidency.

As Rios Montt met with his officers, political leaders of the extreme rightist National Liberation Movement and the centrist Christian Democratic Party worked out a four-point compromise agreement to present to the junta at a meeting they hoped would take place later today.

The candidate of the National Liberation Movement and the man backed by the Christian Democrats in the March 7 elections ran second and third behind Guevara. It was their party's allegation of frauds that the young officers, known to have been displeased with the Army's leadership under Lucas Garcia, used as the excuse to institute their coup.

The joint political agreement was worked out late Wednesday night between the National Liberation Movement's Mario Sandoval Alarcon and the Christian Democrats' Mario Vinicio Cerezo, long bitter political antagonists. It called for elections in six months, a declaration by the junta that its rule was transitory, equal party representation on a new national electoral commission and revision of the electoral laws to guarantee free elections and prevent the sort of frauds that the government's opponents say gave the election two weeks ago to Guevara.

Both Sandoval and Cerezo hoped to present their proposal to Rios Montt in person.

As the debate about elections took place behind closed doors, the main stumbling block appeared to be junta leader Rios Montt, a former presidential candidate who, after four years of imposed exile as a military attache in Madrid, has spent the last four years in Guatemala out of politics, preaching for the Church of the Christians of the Complete Gospel, an evangelical denomination, and running a small grammar school in the capital.

Rios Montt's assumption of power reportedly had not been foreseen by the young officers who staged the coup. He had been brought into the negotiations only for the surrender of Lucas Garcia, who refused to give up to junior officers and insisted that he would hand over power only to a general.

Rios Montt, who had once commanded the Mariscal Zavala Brigade that was the key unit in the coup and had taught many of its young officers when he was head of Guatemala's military academy, is known for his rigidity as well as deep belief in hierarchical formalism within the army and the government. According to well-informed sources, he quickly maneuvered the young officers out of the junta they had already decided on, convincing them of the need for a smaller, three-man junta of senior officers, headed by him.

Since coming to power he has shown few signs of wanting to go along with the younger officers' ideas for quick elections. He reportedly threw away a speech prepared by the young officers Tuesday night and instead addressed the nation extemporaneously, attacking politicians and leftist subversives.

Rios Montt, who charged he was was cheated out of the presidency by an electoral fraud in 1974, has, in the view of several diplomats who know him, emerged as a man who seems to view his sudden rise to the junta leadership from the pulpit of an evangelical church as a God-given right.

His increasingly apparent ambition, his emotional messianic outbursts and his authoritarian style reportedly have angered and worried the young officers and the politicians who have almost unanimously supported the Lucas Garcia overthrow.

"He definitely loves democracy," Luis Martinez Montt, a distant cousin and Christian Democratic Party official said of the general, "but he is so strict that his way of seeing democracy is undemocratic."

"He would probably be a good, benevolent dictator," said Martinez. "He wants everything to go his way."

Ironically the Christian Democrats, as well as the partially underground Social Democratic forces, are also privately arguing for a longer period of junta rule before elections are held.

They fear that early elections would benefit the extreme rightist Natiional Liberation Front.

Cerezo, the secretary general of the Christian Democrats, said he would be satisfied if elections did not take place for a year. He said that would give the country time to prepare truly free elections and would allow his party time to organize a successful opposition to the National Liberation Front, which, supported by rich landowers and businessmen, could benefit from early voting.

Cerezo said his pact with the National Liberation Front had compromised on a six-month wait and that once elections were set, all agreements with the rightist party would be off.