The Soviet Union is greeting US suggestions it is helping stir violence in El Salvador with a crescendo of allegations that Washington may be preparing to invade that Central American nation.
The issue, diplomats here suggest, is tailor-made for a Soviet leadership under fire from the new administration in Washington and under pressure from stubborn unrest in Poland.
How serious the latest dispute between the Soviets and President Reagan becomes will probably depend largely on how Washington handles things. Also curcial will be the reaction of US allies to the current visit to Europe of State Department envoy Lawrence Eagleburger, who is reported to be conveying evidence of Soviet agitation in El Salvador.
But the Soviets are still seen as unlikely to sacrifice what they see as the key issues in relations with Washington and the West -- arms control and trade -- for what amount to propaganda points on Central America.
More important to Soviet leaders were reports that Mr. Reagan will continue the US grain embargo.
The Soviet news media campaign against US policy toward the Salvadoran government has been building for weeks, even before the first US suggestions that Moscow was somehow involved in arming leftist rebels there.
Diplomats said the prominence given reports of US military assitance to El Salvador's rulers indicated an attempt to offset Western media focus on Soviet predicaments in Afghanistan and Poland.
When the nascent Reagan administration began attacking alleged Soviet support for "international terrorism," the Soviets turned to the situation in El Salvador to reply. A genuine popular upheaval was occurring there -- and brewing elsewhere in Central America -- official Soviet media suggested. The US was accused of branding freedom fighters as terrorists.
An article in the government newspaper Izvestia Feb. 17 spoke of growing numbers of "Pentagon advisers" in El Salvador and suggested this might be the prelude to "military intervention by the United States." The newspaper suggested that Mr. Eagleburger was heading for Europe with this in mind.
Diplomats here, meanwhile, differ on pricesely how the Soviets may be aiding Salvadoran rebels. Most analysts speak of a proxy policy, with Cuba as key intermediary. "This makes charges of Soviet interference eminently deniable in Moscow's view," one diplomat remarked.
The Soviets are seen as placing a lower priority on Central America than other areas, such as the Middle East. Diplomats say that, despite vocal Soviet support for the 1979 revolution in Nicaragua, the new regime has had relatively little success in getting economic aid from Moscow.