San Salvador — The United States ambassador to El Salvador says the Salvadorean Army is winning the war here but that progress has been slowed by cuts in US congressional aid.
Ambassador Deane Hinton also asserts that the ''one clear trend'' in El Salvador is a decline in the Salvadorean economy brought on partly by guerrilla sabotage.
In an interview, Hinton said that proposals made by the guerrillas for unconditional negotiations with the US-supported Salvadorean government had proven to be insincere. He said earlier he had been optimistic about the chances for negotiations but that he had been mistaken.
Hinton said that the offer made by the guerrillas to El Salvador's President Alvaro Magana to negotiate have proven to be a ''propaganda stunt.''
''You don't give a proposal through a secret channel to the president of a government and go public in Mexico City in front of television cameras before you get an answer if you're serious,'' the ambassador said.
''To offer a dialogue without preconditions . . . is the single biggest precondition you can have,'' he continued. ''If you said it was a dialogue that was for a return of peace and the democratic process, it would be obvious that it would be a big step forward. But it didn't say that.''
The US and Salvadorean governments insist that any negotiations should deal with entry of the guerrillas into the existing Salvadorean political process. The guerrillas had earlier insisted that the negotiations deal with the sharing of power and the restructuring of the Salvadorean Army and security forces. Those ideas were rejected by the government, and the guerrillas later dropped them as preconditions for negotiations.
Ambassador Hinton said he hoped that a statement made by a guerrilla spokesman, Ruben Zamora, to this reporter, in which Zamora expressed optimism about negotiations, was ''a signal that they're going to change their position and behave seriously.''
The interview with the American ambassador was held on the patio of his residence next to a swimming pool, against a background of chattering exotic birds. When the ambassador makes a move out of his residence in his black Cadillac, no fewer than a dozen bodyguards - both Salvadorean and American - swarm around him.
Ambassador Hinton said that the US was not aiming at a military solution to the war, and that such a solution did not seem feasible ''in any time horizon that makes sense.''
Hinton said the Salvadorean Army did not have enough trained and well-equipped troops to put the guerrillas on the run.
''They don't have the numerical advantage that's necessary to deal with a full-scale insurgency,'' said Hinton.
The Salvadorean guerrillas are estimated to have about 5,000 to 6,000 trained and armed men. The government armed forces, including the Army, Navy, and Air Force, have about 20,000.
''They were building up,'' said Hinton. ''They were going to train new battalions, but the Congress didn't appropriate the funds. It just makes the war go on longer.
''A $35 million supplemental military assistance package did not go through the Congress,'' the ambassador said. ''They asked for $60 million for fiscal year '83 appropriations, and at this point, we have $25 million.''
''That's $70 million short,'' he said. ''And that just means that the training of new units, the formation of new units, and the equipping of new units just doesn't happen. . . .
''We've disbursed about $80 million in military funds in 1982,'' said Hinton. ''That was the $25 million plus $55 million in presidential contingency funds which largely went to redo the Air Force and train the battalion at Fort Bragg and the cadets at Fort Benning.
''It's not a lot of money by Pentagon standards. It doesn't buy very sophisticated things. It looks like a lot in this context. But it doesn't go very far in the middle of a war.''
The ambassador said that more and more supplies were being flown in to the guerrillas by air but that there was no easy way to stop this. An air defense system for El Salvador would cost more than $100 millon, he said.
In Hinton's view, the war is going to be won by ''some fellow on the ground with a rifle.''
Aside from blocking a guerrilla takeover, the ambassador thought that El Salvador's priorities in the coming year should be to:
* Complete a new constitution and work toward new elections, including direct elections for a president;
* Stop a decline in the economy which is now in its fourth year;
* Reduce violence and human-rights abuses through judicial reforms and other means;
* Maintain economic and land reform programs as well as an educational and health system in the face of a need for enormous budget cuts.
El Salvador, Hinton said, has got ''all of the problems of a developing country'' in addition to problems created by a war and the needs of hundreds of thousands of displaced people.