Christian Democratic leader Jose Napoleon Duarte became president of El Salvador today in a major restructuring of the embattled military-civilian coalition government. But the key question of whether the military can now be brought under control remains to be answered.

Duarte was elected president in 1972 but never served because the ultra-rightist Army of the time, in collusion with the small economic elite, voided the results. Duarte spent more than seven years in exile in Venezuela.

Diplomatic sources said the U.S. Embassy is prepared to recommend renewal of recently suspended aid in view of the reorganization.

Col. Jaime Abdul Gutierrez, who served with Duarte in the five-member junta, now effectively defunct, will become vice president and commander-in-chief of the armed forces, according to an official government communique.

The communique also called for formation of a counsel of state with representatives of peasants, workers, business and professional sectors and renewal of "efforts to bring about a dialogue with all political forces, including those who have taken up arms."

In addition, government and diplomatic sources said that all but one member of the Cabinet will resign or change his post. The compromise response to the deep political crisis has several aspects that appear to favor government conservatives.

The one Cabinet minister who reportedly remains is Defense Minister Col. Jose Guillermo Garcia, despite repeated accusations by leftists and suspicions on the part of the U.S. diplomats here that he has no willingness or ability to curb terrorism by his troops.

Charges of official security-force involvement in political violence that has taken at least 9,000 lives this year have brought the government to the brink of collapse twice, although Garcia repeatedly has said he is doing the best he can.

Crucial U.S. aid was suspended earlier this month amid allegations that elements of the military were implicated in the killing of four American churchwomen and five prominent leftist leaders.

For more than a year, the government has had to cope with an increasingly well-armed, leftist guerrilla movement now allied with a growing number of moderate leftist political, professional and union groups.In the last two months, it has also faced the possibility of an extreme right-wing takeover.

Sources said Col. Nicolas Carranza, the vice minister of defense who also has been a focus of charges that the government has sanctioned right-wing terrorism, will be relieved of his post. Carranza had been in charge of day-to-day operations by the Army and security forces.

For the last nine months, the executive has been a five-member junta composed of two Christian Democrats, Duarte and Jose A. Morales Ehrlich; two colonels, Gutierrez and Adolfo A. Majano, and an independent, Dr. Ramon Avalos Navarrete.

According to the government communique, the junta technically will remain intact, except for Majano, widely considered its most liberal if not always its most effective member. He was removed from the junta by a vote of the armed forces a week ago and will receive a diplomatic post, sources said.

U.S. diplomats here, who have backed the government in its various forms since the coup 14 months ago were cautiously optimistic about today's announcements.

"This is an effort to end the squabbling and divisiveness," said one senior diplomat. "But once you've got stability, will the programs that are begun or hoped for, like the reforms and human rights, be carried out? Will there be a decline in right-wing violence? That's what we want to see."

The restructuring came after a series of marathon meetings between the Christian Democratic Party and the military.

Earlier this week, Duarte said he believed "what we need in El Salvador is law and order. We have become like the Wild West with the law of the revolver. It is not important who is in or who is out of the government. The most important thing is how we can solve the basis of the problems, the violence. Whoever has the capacity to do this should have the power to do it."

Duarte said the Christian Democrats had agreed to remain in the government on conditions that were centered on "complete control of the Army." Unconfirmed reports of more specific demands for the removal of Garcia and Carranza circulated throughout the week. Majano and some U.S. diplomats said they believed the first step toward eradicating military abuses would have to be the removal of these two figures.

But Duarte, who entered the junta in March, has demonstrated determination to get along with his soldier colleagues.

Some diplomats and politicians have suggested he may also have intent on furthering personal ambitions.

"Duarte has consummated his dreams but he's made an expensive compromise," said one influential foreign observer. "If the president is not the commander-in-chief and can't give the orders, he's not in command. These civilians are just being kept as figureheads. There will be more violence now because the Army now has more power to go all out against the left."

Although Salvadorean leftists credit Duarte with once having been a major liberal opposition leader, they now denounce him as a mere "sergeant" carrying out the orders of military sponsors.

There is not any concrete indication that the left will be more disposed to negotiate with Duarte as president than it was with the junta on which he served. There is evidence that the generally conservative middle class is inclining toward supporting him.