Reagan, Lopez Portillo head toward a middle ground on El Salvador

When Presidents Jose Lopez Portillo and Ronald Reagan get together June 8 and 9 at Camp David, the agenda is likely to be a long one. One item near the top will be El Salvador: The two countries have overtly differing perceptions on the troubled Central American nation. Mexican and US officials indicate the leaders will also talk about trade issues, fishing disputes, undocumented workers, and other border troubles.

There has been a steady flow of communication between Mexico and the United States over all these issues, but in recent weeks El Salvador has become uppermost. Despite differences in their positions, a movement toward a middle ground is clearly under way.

The Reagan administration came to office 100 days ago arguing that leftist, Cuban-backed insurgency in El Salvador was the chief cause of violence there and the key threat to peace in the area. A much-disputed "white paper" issued by the nea Reagan administration accused Cuba of shipping tons of arms and ammunition to leftist Salvadoran guerrillas.

To counter the Cuban efforts, Washington gave unstinting support --both military and economic -- to the government of Salvadoran President Jose Napoleon Duarte. The US aid included both military equipment and military advisers.

All this ran counter to the Mexican view -- and incidentally to the views of much of Latin America -- that El Salvador's social and economic inequities were the root causes of its malaise, and that military aid to the Duarte government was wrong. Mexico also said the Salvadoran government was to blame for much of the violence.

Mexico has officially tended to support the leftist political and guerrilla causes in El Salvador, responding in part to a belief that these causes were likely to win out in the end. Also behind the Mexican stand were domestic considerations --with support for Salvadoran leftists acting as a sop to the political left in Mexico.

But Mexico, in a way, was hedging all bets.While overtly supporting the leftist guerrillas, the Lopez Portillo government has also lent President Duarte a great deal of quiet support. For example, it has continued to send sizable shipments of petroleum products to the Salvadoran military.

Now, Mexico and the US have begun to find some common ground on the El Salvador question. The US, in some measure responding to prodding from Mexico and other Latin American nations, is letting the Duarte government know of its displeasure over violence that springs from military and paramilitary activities.

At the same time, Mexico is putting pressure on leftist political groups to consider a negotiated settlement with the Duarte government and on leftist guerrillas to scale down the fighting -- arguing that the social a nd economic programs of the Duarte government are having some effect and that a military victory is unlikely.