Presidential assistant Zbigniew Brzezinski warned Iran last night that its "national integrity" as well as its well-being are increasingly jeopardized by the continued captivity of 53 Americans in Tehran.

In an interview on public television's McNeil-Lehrer Report, Brzezinski said part of this threat arises from reports of "a steady buildup of Soviet bases in the Transcaucasian military district" on the Soviet Union's side of its border with Iran.

"Growing tension between Iran and Iraq" was also cited by Brzezinski as an indication of intensified danger to Iran.

The White House national security affairs adviser declined to discuss possible U.S. action against Iran such as mining or blockading its coast, which have been under discussion in the Carter administration as a last-resort means of exerting pressure for release of the hostages.

But Brzezinsksi said that if the situation in Iran continues, that country may confront "danger of partition." This suggests that various external forces, including the Soviet Union, Iraq and possibly other countries, might help themselves to portions of a lightly defended and chaotic Iran.

Brzezinski's discussion of the dangers of Iran's security, volunteered repeatedly in the course of the television interview, made explicit and open the "background" comments of high White House officials in recent weeks. This line of discussion appeared to be an attempt to convince Iranian authorities that they have something important to lose by continuing to hold the U.S. hostages and remaining in conflict with Washington.

Intensified Soviet troop movements near the Iranian border were first reported by U.S. officials in February. White House sources said last night that Brzezinski was referring to a continuation of field maneuvers and a gradual buildup of understrength Soviet border units near Iran, the same sort of activity that was reported two months ago.

Moscow denounced reports of the Soviet movements at that time, saying this was "fantasy." Iranian authorities displayed little reaction at the time, maintaining that their army and population would thwart any outside threat.

Brzezinski's comments came amid increasingly open signs of impatience among senior administration officials at the long-running stalemate over the hostages.

Brzezinski was asked if President Carter might take further nonmilitary steps against Iran as early as next week, as hinted by another high White House official. "This is not to be excluded," he replied.

The timetable for future U.S. action remained vague, although officials indicated that U.S. allies in Europe and Japan have been asked to place strong economic sanctions against Iran in the immediate future and to break diplomatic relations with Iran in mid-May if the economic pressure do not bring about the release of the hostages.

Asked if the United States would wait until June -- considered the earliest date for a decision on the hostages by the future Iranian parliament -- Brzezinski replied, "I would rather doubt it."

Echoing Carter's words in an interview with European television networks -- broadcast Sunday -- Brzezinski said, "It's not a matter of months, it's a matter of weeks at most" before the United States will be faced with taking strong new action.