Salvador -- shift from junta to presidency?

El Salvador's 14-month experiment at joint civilian-military government is about to undergo a change -- with Jose Napoleon Duarte, the leading civilian in the government, emerging as the country's president.

That, at least, is the scenario evolving in high-level circles in El Salvador.

The arrangement is the latest effort to bring about a viable government in the embattled Central American country. Sources close to the present administration say that Mr. Duarte would immediately seek international help at mediating El Salvador's civil war. It is understood that Mr. Duarte has begun looking for mediators -- and has approached Colombia, Costa Rica, Nicaragua, Panama, and Venezuela.

Whether the country's leftists and rightists will accept such mediation remains to be seen, but there is evidence that elements from both left and right might join in a such an effort.

The situation in El Salvador is very fluid. The 14-month-old junta with its three civilians and two military men is clearly no longer viable. Although it had made headway in recent months against both leftist and rightist extremists and enjoyed the staunch support of the United States, the junta was facing a great many internal pressures.

Moreover, the sacking of one of the military men by his fellow officers last weekend was evidence of the growing strains in the junta and in the government in general.

Replacing the junta with a single executive would mark an effort to solve those strains.

Under the new arrangements, Col. Jaime Abdul Gutierrez is slated to become commander in chief of the Salvadorean armed forces.

Both Mr. Duarte and Colonel Gutierrez are members of the junta that has ruled El Salvador since Oct. 15, 1979, when young Army officers overthrew the military government of Gen. Carlos Humberto Romero. Gutierrez was one of two officers who joined the junta at that time.

Mr. Duarte joined the junta in January of this year. He is head of El Salvador's centrist Christian Democratic Party. He was considered the victor in 1972 presidential balloting, but the military of that era prevented him from becoming president.