The Soviet Union is not likely to invade China if the Sino-Vietnamese border war remains essentially on the present scale, the State Department's top Soviet expert said yesterday.

Marshall D. Shulman, special adviser on Soviet affairs to Secretary of State Cyrus R. Vance, also told a conference of newspaper editors and broadcasters that "there have been no indications" of Soviet preparations for action against China along the long border between the two rival giants of world communism.

Shulman also said, however, that it is not clear to the United States how far the Chinese are prepared to go in the current invasion of Vietnam. Thus he did not rule out a Soviet countermove if China moves deeper into Vietnam to threaten or attack the Hanoi-Haiphong area.

There is growing concern among some Carter administration officials about Soviet options which fall short of full-scale retaliation across the Sino-Soviet border, yet which could create new instability in Asia. Among these is the possibility that Moscow could use the Chinese threat as a lever to obtain from Vietnam rights to establish naval or air bases at the former U.S. facilities at Camranh Bay or Danang.

Such Soviet bases, in the view of some White House and Pentagon officials, would engage U.S. "vital interests" by making possible the projection of Soviet power to East Asia as never before. As in the case of the Soviet bases in the Indian Ocean, such facilities could increase Moscow's challenge to U.S. and allied fleets and forces. Administration sources said Moscow has been informed of U.S. concern about the matter.

Other Soviet options short of an invasion of China include a strong campaign against Chinese aggression in world opinion, conspicuous "consultations" with Vietnam about the Chinese attack as called for by the Soviet-Vietnamese friendship treaty of last November, and stepped-up military and economic assistance to Hanoi.

American officials discounted reports of major Vietnamese troop movements aimed at engaging the Chinese forces, saying that intelligence from the field has not disclosed such a push. The officials said Vietnam has so far been careful not to deploy large forces outside the area protected by surface-to-air missiles, originally installed to protect the capital region and sensitive facilities against American warplanes.

So far both China and Vietnam have carefully limited their use of airpower in the border conflict, according to American sources. A decision by either side to unleash warplanes against the other's large-scale troop concentrations, capital or heartland would signify a major and dangerous escalation of the war, in this view.

On the diplomatic front, State Department spokesman Hodding Carter announced that the United States "strongly favors" a meeting of the United Nations Security Council to consider "all aspects of the situation in Southeast Asia, including both the Chinese invasion of Vietnam and the Vietnamese invasion of Cambodia, as well as the need to prevent a wider conflict."

Carter said the United States is consulting other governments about a Security Council meeting, which is considered likely later this week.

None of the powers directly involved has called for a Security Council meeting of this nature. Vietnam and its ally, the Soviet Union, would like to see United Nations discussion of the Chinese action but oppose taking the Cambodian situation to the world body. Just the opposite situation prevails on the Chinese side.

By linking the two conflicts in the call for United Nations action, Washington is pursuing something of an even-handed treatment of the rival communist powers. Carter, under questioning by reporters, said the two invasions are linked "to the extent that there are two threats to the peace of the region... two assaults across a territorial border."

Spokesman Carter said he saw no deep significance in his use of the term "invasion" about both the Vietnamese and Chinese actions, while President Carter in an address on Tuesday called the Vietnamese action an "invasion" and the Chinese action a "frontier penetration."

Shulman, in his remarks to the editors and broadcasters, said the conflict in East Asia could impair "the degree of intimacy" between the United States and China "unless the aggression is terminated," although he said the normalization of relations will continue. Shulaman also said the war had clearly set back the chances for early normalization of U.S.-Vietnamese relations.

Some U.S. officials believe there are signs that the Soviet Union is withholding approval of final terms of a new strategic arms limitation treaty (SALT) while the Chinese invasion of Vietnam continues. The Soviets have charged through press organs, most recently a Pravda article published yeaterday, that U.S. "circles" encouraged the Chinese attack during the recent visit here of Vice Premier Teng Hsiao-ping.

On the other hand, other American officials said there is yet no sign that the events in Asia have impaired completion pletion of SALT II. These officials said the U.S.-Soviet discussions about SALT continue to inch toward final agreement, and described Soviet responses to U.S. proposals in recent days as neither unusual nor discouraging.