Soviet Defense Minister Dimitri Ustinov today promised that Moscow would help India meet any threat arising from U.S. arms sales to Pakistan.

Ending the six-day visit to India of the largest and highest-ranking military delegation the Kremlin ever has sent outside the East Bloc, Ustinov beamed as he answered a question on future Soviet weapons sales to India.

"Everything will be all right, be sure," he said before he and his delegation of more than 30 generals and admirals returned to Moscow.

G.K. Reddy of the Hindu newspaper, one of the best-informed Indian journalists on diplomatic and defense matters, reported today that the Soviets have offered top-of-the-line equipment at cut rates and soft terms.

Although the Indian government has tried to downplay the Ustinov visit as routine, there has been wide speculation among nongovernmental Indian defense analysts and diplomats here that his mission was to scuttle India's announced plan of diversifying its arms supplies by purchasing Mirage 2000 jet fighters from the French.

Whether Ustinov was successful remained unclear today. An Indian cancellation of the French deal, in which a preliminary letter of intent has been signed, could cause a breach in the increasingly warmer relations between India and the new Socialist government of Francois Mitterrand. One of Mitterrand's special advisors, Jacques Attali, has been here talking to top Indian officials during the Ustinov visit.

Nonetheless, as Reddy's report indicated, it appears likely that the Indians will be getting additional Soviet arms in the future, even if New Delhi continues with the Mirage deal.

"No longer is there a generation gap between the military equipment that is being offered to India and the latest weaponry that is currently in use with the Soviet front-line formations in Europe," Reddy wrote.

Furthermore, India no longer has to beg the Soviets for advanced weapons systems, he added, since "Moscow is offering them. It is for India to pick and chose from the whole range of the latest Soviet-made equipment . . . . "

Among the new weapons the Soviets are reportedly ready to supply India with are the T82 tank and the Mig27 "Flogger" tactical strike fighter that is reputed to be equivalent to or better than the Mirage 2000.

These new purchases would come on top of a $1.6 billion Indo-Soviet arms deal in 1980 that is reported actually to be worth three to four times more because of sweetheart pricing and financing arrangements made by Moscow.

Since then, however, the Indians have sought to diversify their arms supplies by purchasing Jaguar jet fighters from Britain and submarines from West Germany.

The diversification appears to be an important element in the foreign policy of Prime Minister Indira Gandhi. She has emphatically denied in recent interviews that India is pulling too close to the Soviet Union because of the arms supply relationship and New Delhi's equivocation on Moscow's invasion and 26-month occupation of Afghanistan.

Furthermore, the United States is known to have told Gandhi that the more India acts truly nonaligned, the more understanding its views will get from the Reagan administration.

One diplomat who is well-informed on Soviet affairs said this is the first time he can recall the Kremlin sending out its defense minister as an arms salesman.