The Carter administration has publicly promoted, funded and defended a military-civilian coalition government here for the past seven months, hoping that it could build a middle road between political extremes that have torn this strategically located Central American country.

But in recent weeks, the U.S. backed government in El Savador has taken a visible swing to the right, and the United States, appearing irrevocably committed to the ruling junta, has been forced along.

Several recent developments suggest the most conservative elements of the government have the upper hand:

The release of the country's most radical rightist leader -- who was arrested for plotting a coup -- by the armed forces.

The increasingly aggressive posture of the military, including the storming of the National University last week.

The action of some military units to subvert government reform programs.

Human rights are still a concern here, but in the current warlike atmosphere less concern is shown for them.

If the trend continued and violence here does not diminish, said one senior U.S. diplomat, "United States policy [of promoting the ostensible middle to avoid an extreme takeover] in El Salvador is going to fail."

The move to the right has been caused by several factors including the intransigence of the leftist revolutionaries seeking to oust the ruling junta, the growing power of more hard-line military officers and the decision of some members of El Salvador's conservative private sector to work with the government rather than fight it.

"We've got the power but no choices," said one U.S. official when talking about Washington's role. Using hyperhole that has become a standard policy line to make a point he asked, "When you've got the Pol Pot left and the feudal right, where do you go?" Pol Pot is the radical former leader of Cambodia.

Since an Oct. 15 coup in which progressive military officers ousted a hard-line Army president and invited liberal civilians to join them in a governing coalition, the Carter administration has tried to bolster the military in its fight to contain the left and tried to undercut its still largely rightist dominated ideology by promoting widespread social and economic reforms. The reforms are designed to take some of the steam away from leftist appeals to El Salvador's oppressed peasants and laborers.

An early plan to send in U.S. Army specialists to help train El Salvador's security forces in pursuing leftists while avoiding mass repression was shelved. State Department and congressional opponents charged it bore a marked resemblance to counterinsurgency training abroad that had been discredited as policy in recent years and it risked giving a boost to the "anti-imperialist" cause of the leftists.

The United States has pledged $50 million in economic aid and nearly $6 million in military assistance -- primarily communications and transportation equipment -- to the current government.

U.S. officials believe these funds will claim military fears that Washington has abandoned El Salvador and thus increase the State Department's leverage over the armed forces. The military, it is hoped, will then be compelled to take a moderate position and civilians in the government will be assured.

Although many Christian Democratic officials have quit in arguments about whether to continue the party's association with the military, the party is still officially participating in the junta. While the remaining party members have been close to mass resignation twice in the last six weeks, reforms are still being publicly advocated by the government.

A fundamental aspect of the Carter administration's position here is support of sweeping changes in El Salvador's narrow distribution of wealth. With constant State Department prodding, the government has implemented massive agrarian reforms, nationalized the banks and taken control of foreign commerce. The government thus hopes to eliminate the most attractive promises the leftists have to offer.

Even some of the more conservative members of the military here, including the powerful Defense Minister Jose Guillermo Garcia, say they recognize the wisdom of this policy. In any case, one added, "The reforms are now irreversible."

Yet in a society that has been systematically destablized by extremists and by elements within the government, nothing is certain.

A major Salvadoran newspaper, El Diario de Hoy, suggested in a recent editorial that the reforms should be recognized as failures and completely reconsidered.

More seriously, on at least two occasions in the last month apparent members of the Salvadoran military have driven to government-sponsored agricultural cooperatives, which are an essential part of the reform program, and summarily killed cooperative leaders deemed to be leftist subversives.

The government denies that its security forces took part in the murders. Some officials say the troops might have been guerrillas in stolen uniforms. Garcia says an investigation revealed that the National Guard only arrived after the event at the largest massacre.

But eyewitnesses report that on the San Francisco Guajoyo cooperative, where 12 people were killed May 29, the soldiers who did the shooting were wearing complete National Guard uniforms, helmets and flack-jackets, carried government issued rifles and arrived accompanied by a government armored car.

"The military is back to the old ways," said one bitter land reform official.

Similar fears are expressed by some members of the U.S. Embassy staff.

Christian Democratic leaders in the government, members of the military and United States Ambassador Robert White insists, however, that the situation here is actually improving. The left already has been weakened by the reforms and the Army recognizes this, they maintain. But the intransigence of the leftist leaders and the necessity to restore order to a country where violence has provoked increasing chaos, dictates a need for unity with whatever sectors of the society are willing to compromise. The right, they say, except for a very few extremists, has recently shown itself willing to do so.

"I came down here with the great hope that there was a rational left down here," said White. But when he arrived in March, the leftists, even former moderates, were committed to armed revolt as the only sure way to change Salvadoran society. Reinforcing this stand was the fact that most of the moderate leftists who might have acted as a bridge between the government and the extreme Marxist factions were murdered or forced out of the country by rightist death squads.

Both the embassy and the government have held secret talks with certain leftist organizations, especially the United Popular Action Front and its guerrilla wing, the Armed Forces of National Resistance, according to sources on both sides.

But a steadfast demand of the leftists is that the Salvadoran armed forces be dissolved and reintegrated with the guerrillas in command, a point on which the military clearly feels unable to compromise.

The right, some believe, has become more tractable.

"I don't want to claim too much," White said, "but there are some faint signs that the private sector has made the decision to live with the [current government] situation and that the private sector has decided that the government has indeed projected a sense of permanence and they have to go back to work."

But as violence continues to increase here, the military is likely to have more freedom to take whatever measures it considers necessary to restore order. If this takes the form of increased repression, which Garcia regards as a "relative concept," the Christian Democrats and the United States may have no choice but to go along for the ride, or withdraw and lose all influence. Ultimately, some diplomats and moderate officials here worry, they may have no choice, and no power either.