President Hafez Assad's recent visit to Moscow has overcome a year long strain in Syrian-Soviet relations and produced new pledges from Moscow to strengthen Assad's military force for confrontation with Israel, Syrian officials say.

Their optimistic tone in describing the latest negotiations is regarded as particularly significant in light of Syrian pledges to resist Israeli air raids and reconnaissance flights over neighboring Lebanon. Syrian and Israeli jets have clashed three times since June in Lebanese skies. Fighters from both sides continue to fly regular patrols at dangerously close quarters, leading analysts here to conclude more such dogfights are likely.

A Syrian delegation headed by the defense minister, Maj. Gen. Mustafa Tlas, and the chief of military procurement, Maj. Gen. Assad Mokaid, is reportedly still in Moscow working out military deliveries that, according to hints from Syrian officials, were worked out in principl during Assad's stay.

No specifics are available here on what new weaponry Syria is getting, in line with Damascus' traditional secrecy on military matters. But military analysts believe Assad were especially seeking more Soviet fighters, particularly Mig25s and Mig27s, to make his pilots more of a match for the Israelis' U.S.-supplied F15.

Syria's need for more sophisticated fighters with improved electronics was demonstrated in deadly term in two dogfights pitting Syrian Mig21s against the F15. Last June, in the first fight, Syria lost five planes. In the second, late last month, it lost four more. Israel reported no losses in either clash.

In addition, two Syrian Mig23s shot air-to-air missiles at an Israeli F4 Phantom on a reconnaissance mission over Lebanon on Sept. 19 -- and missed.

Despite the losses, the Syrian government has made clear its determination to prevent Israeli jets from roaming over Lebanon and attacking Palestinian concentrations there with impunity. The government-controlled Damascus press has said Syria's air defence umbrella now extends into Lebanon, where more than 20,000 Syrian troops have been stationed as peacekeepers since 1976. Syrian anti-aircrafts batteries are visible at many Lebanese intersections.

Despite, the one-sided scores in clashes with Israeli fighters, Syrian Air Force officers and government officials are reported to be encouraged by the shooting down Oct. 7 of an unmanned Israeli reconnaissance drone. The kill, by Mig21s firing missiles about 50 miles north of Damascus, was seen as a demonstration of radar tracking capability and the Mig pilots went on Syrian television to trumpet their victory.

In addition some Syrian officials have said the most recent dogfight with Israeli fighters included the downing of an Israeli F15 and an F4 Phantom. The claim has been denied by Israel, but diplomats here reported it has served as a morale-booster in the Syrian Air Force.

Assad's government is aware, however, that it is at a disadvantage against the Israelis flying F15s aided by U.S.-made flying radar platforms. The backbone of the Syrian Air Force is 12 interceptor squadrons with more than 200 Mig21s, according to reliable Western estimates. In addition, Syria is said to have 50 of the most advanced Mig23s and a dozen Mig25s. But as far as is known the Mig25s have not been sent up against Israeli planes, and the Mig23s only infrequently.

It was Assad's insistence that Moscow fill the weaponry gap between Syria and Israel to establish a strategic balance after Egypt's withdrawal from the Arab front lines that led to chill in relations with the Soviet Union last year.

The Syrian leader, a former pilot and Air Force commander, visited Moscow a year ago in search of more sophisticated arms.

But his chief of staff, Maj. Gen. Hikmert Shihabi, walked out on followup talks several weeks later, when it became apparent that the Soviets were not prepared to meet Syria's requests.

At the same time, friction was reported among Syrian soldiers and the estimated 3,000 Soviet military advisers here.

For a time, sources say, battalion-level advisers were withdrawn to higher command levels to allow tensions to subside.

Assad was miffed again last June, when the Soviet Union put off his planned visit to Moscow. The Soviets cited President Leonid Brezhnev's health but, coinciding with a sectarian massacre in Syria, the delay was ill-received here because some interpreted it as a sign that Assas was unwilling to leave amid the tensions at home.

Nevertheless, the Soviets delivered about 65 T72 tanks whose sale has been agreed upon earlier.

In arguing against immediate delivery of more sophisticated arms, Moscow reportedly urged Assad to take advantage of what looked then like increased cooperation with Iraq.

The 212,000-man Iraqi armed forces are well-trained and equipped, and there was talk of stationing some units on the Golan front as a sign of solidarity.

Since then, however, the plans for Syrian-Iraqi military coordination have been shelved because of new tension between the traditionally rival Baath leadership in Bagdad and Damascus. In addition, the Soviet Union apparently has been convinced of Syria's increased needs as what one diplomat here called "the only Arab state actually confronting the enemy."

A communique issued at the close of Assad's visit cited "a decision to continue strengthening Syrian defense capabilities." Although the talks going on now remain incomplete, Assad's aides interpret the decision as a victory and a sign that relations with Moscow have improved. One of the best ever."