The State Department reacted favorably yesterday to a statement Thursday by President Carlos Humberto Romero of El Salvador announcing a general amnesty for political exiles and inviting the Organization of American States to send observers to verify the fairness of next year's congressional elections.

In the past, the State Department has been critical of human rights abuses by the Romero government.

Escalating civil violence and open political protests have made the Salvadoran military regime fearful that it may face the same fate as Nicaraguan President Anastasio Somoza, who was ousted this summer after years of insurrection. It was that fear, according to observers, that prompted that government to announce the reforms.

Romero, who claims El Salvador has no political prisoners, also invited the Red Cross to inspect the nation's jails to see for itself if his words are true.

"We consider these positive measures, which should reduce tensions and establish credible democratic processes," State Department spokesman Thomas Reston said yesterday.

In 1976, El Salvador, along with Brazil and Guatemala, turned down all U.S. military aid after the Carter administration announced that such aid might be withdrawn as a sanction against human rights violations. El Salvador and Guatemala later reconsidered, and made it known to the State Department that they would accept such aid if offered. Defense Department and intelligence representatives have argued that military aid should be reconsidered, and that the United States should try to assist El Salvador's armed forces to prevent the fall of Romero.

But one State Department source said that the effort might be wasted on a military regime which many administration officials believe is unsteady.

"The administration is very concerned about increasing polarization in El Salvador and has engaged in intensive diplomatic efforts to try to encourage the Romero government to liberalize," he said. But such attempts may be "too late," he added, because of Romero's poor human rights record.

A State Department report to Congress early this year charged that Salvadoran security forces used torture, including electric shock and rape, on prisoners. "There have been no public investigations of these charges," the report added.

The State Department has also accused the Romero government of manipulating and falsifying the elections of 1978.