The presence of Soviet arms and military advisers in North Yemen is increasing steadily, and the government says it has no intention of stopping the flow despite concern in Saudi Arabia and the United States.

The influx grows from determination within President Ali Abdullah Salah's government and officer corps to strengthen the armed forces from whatever sources are available to a country with Yemen's limited financial resources.

It reflects a history of military aid from the Soviet Union combined with North Yemen's resolve to remain independent of its wealthy Saudi neighbors, whose attempts to steer the Sanaa government away from Moscow often have been heavy-handed.

Against this background, President Carter's decision in March 1979 to dispatch under emergency procedures 15 Northrop F5E fighters and 64 M60 battle tanks, a gesture urged by the worried Saudis, appears now to have been too little, too late and too closely tied to Saudi Arabia to make a difference in North Yemen.

Instead, the size of the direct Soviet effort has largely eclipsed the U.S. arms and their value as a symbol of Western and Saudi support.

If North Yemen is weaned away from Saudi Arabia and the West, it would represent a major setback for American efforts to contain Soviet influence in the Middle East, right in the backyard of the world's leading oil exporter. Outright alignment with the Soviet Union by North Yemen would be seen elsewhere in the Arab world as another loss of face and influence by the United States on top of developments in Iran and Afghanistan.

In addition, North Yemen is strategically placed to provide a possible site for military control of the mouth of the Red Sea.

Soviet ships are regularly unloading Mig 21 and SU22 warplanes along with T55 tanks and other military equipment at this humid Red Sea port -- even as Yemeni pilots learning from two American instructors make practice landings in the F5Es at Sanaa airport 150 miles northeast.

Migs and Sukhois, painted in camouflage, line up at the main airport here. Nearby on the coast, a Soviet-supplied radar and antiaircraft battery rises beside the road stretching along a 12-mile sandspit protecting Hodeida's deep-water harbor where the Soviets land their arms.

Analysts in the capital estimate that North Yemen has received 15 SU22 ground-attack jets and 10 Mig 21 fighters since February in a deal in which Moscow has promised 40 Mig 21s and 20 SU22s.

In addition, soon after the American tanks began arriving, Soviet T55 tanks started showing up. First came 200 Polish-made T55s, military analysts say, and since then at least 300 more from the Soviet Union's own stocks.

Also recently arrived from the Soviet Union, they say, are 65 multiple rocket launchers and 18 self-propelled antiaircraft guns, with four 24 mm cannons that spit out 900 rounds a minute.Moreover, 70 armored personnel carriers sent by Carter have been joined by Soviet armored cars.

Along with the weapons have come Soviet military experts to train Yemenis in their use. About 230 Soviet military advisers are reported to be working in North Yemen. The schedule of future arms deliveries has led to predictions that the number will rise.

Up to 70 U.S. military personnel were in North Yemen last year to train Yemenis on the American weapons. But that number has dropped to eight, including the two instructor pilots, U.S. sources say, in addition to U.S. teams that come and go and a dozen civilian technicians.

It was because Saudi Arabia urged and financed the deal for American aircraft to strengthen North Yemen against Marxist South Yemen that the Saudi rulers became particularly upset when the Soviet arms started coming. Their worries were heightened by talks that for the first time showed signs of improving relations between the Marxists in Aden and the Sanaa government.

Since then, North Yemen has offered repeated assurances to Saudi Arabia that the flow of Soviet arms and advisers does not mean a change in Sanaa's traditional policy of non-alignment, and that the unity talks do not mean a drift toward a Soviet-oriented alliance with the south.

But Prime Minister Abdul Azia Abdul Ghani and Foreign Minister Hassan Makki said in separate interviews this week that the North Yemeni assurances have not included a specific promise to send the advisers home as reported last March in Saudi Arabia.

"Everybody got angry, but we thought they shouldn't," said Abdul Ghani. "We have got arms from the Soviet Union since the 1950 . . . As long as there is a job to do, there will be advisers to do it."

Echoing this theme, Bakke said: "We have our own interests. They have their own interests. They are our neighbors, but our interests may not always be the same. I will never say to them [the Soviets] not to come because somebody is not happy that they are here. I will never accept that someone tells us how to deal with other countries."

At the same time, both officials emphasized that Salah's government has assured the vigorously anticommunist Saudis that the Soviet advisers are in North Yemen only for weapons training and maintenance, and that their departure will be considered when their job is finished.

"We gave all these assurances that there is no shift in policy," the prime minister said. "The equipment is equipment whether it comes from the United States of the Soviet Union."

Saudi Arabia nevertheless became so irritated about the Soviet arms deal and the unity talks that it unofficially suspended aid to North Yemen in December and January. As a result, some soldiers and civil servants got paid late.

Independent sources estimated that the Saudi government and royal family distribute $250 million as budget aid annually to North Yemen and a similar amount for special development projects and discreet payments of their own to ministers, officers, and tribal sheiks whose influence is considered valuable in Riyadh.

Jarred by the halt in Saudi funds, Salah sent envoys to Saudi Arabia to try to repair the damage. A Yemeni diplomat said Salah authorized Makke to tell them that "in principle" North Yemen accepted a phase-out of the Soviet advisers.

After the talks the Saudis resumed their aid. Nothing was said about when the advisers would leave, however, the and Yemeni diplomat said there are no signs this will be soon.

Anxious for more definite word, the Saudi defense minister, Prince Sultan ibn Abdul Aziz, and foreign minister, Prince Saud ibn Fasal, paid an unusual joint visit to Sanaa May 13 for talks with Salah.

Abdul Ghani and Makke both said thie review of Yemeni-Saudi relations satisfied the Saudis, ensuring continued aid. Several diplomats in Sanaa have noticed signs of another potential cash pinch in the government, however, and they say Sultan and Saud flew home with less of a guarantee than they had sought.

The Saudis traditionally have thought of North Yemen as a close ally and a buffer against Soutn Yemen, ruled by Marxists and closely tied to the Soviet Union. Thus their nervousness remains close to the surface as North Yemen deals directly with the Soviet Union and improves its relations with Aden.

The obligation to deal with Washington through Saudi intermediaries has irritated the independent-minded Yemeni government. A high Yemeni official complained that at one point in the training program every U.S. instructor was accompanied by a Saudi "as if the Americans did not know what they were doing by themselves."

By contrast, the Soviet Union has made a point of direct contacts and swift fulfillment of its promises. Yemeni officials said Moscow even diverted an arms ship at sea on its way to another country to make sure one shipment arrived in Yemen before deadline.