Amid mounting suspense about the deliberations in Tehran, Carter administration officials said yesterday that Iran has been repeatedly informed in recent weeks that less than a full release of American hostages would not be in the national interest of either country.

As the Iranian Majlis, or parliament, prepared to begin its debate on the hostage issue, administration officials said they have no reliable assurance from any source about the outcome. It was the common belief among policy-makers, however, that the Majlis decisions will be crucial to the immediate future of the lengthy hostage standoff.

Even as they publicly declared that it would be unwise to raise expectations, officials conceded that the government is busily updating and refining long-established contingency plans for a release of some or all of the hostages. If and when they are released, the hostages are expected to be flown to a U.S. military hospital in West Germany for several days of rest and tests before returning to the United States to meet their families and the American public.

Causing concern in official quarters was a new spate of public suggestions by Iranian figures of several different factions that a partial release, rather than a release of all 52 Americans, is being discussed. Washington policy-makers said they have had no official word from Iran, either directly or through intermediaries, that such a plan is being considered, but they added that unofficial suggestions of a partial release have prompted a series of U.S. messages on that subject this fall.

The administration position is that a release of some hostages while others remain in confinement would be extremely complex in its implementation and might well create the opportunity for militants in Tehran to torpedo the release of the remaining Americans. President Carter would find it difficult to meet any of the Iranian demands while some Americans are still held. And from a polticial viewpoint, a partial release would leave Carter with the problem of captive Americans still unsolved.

President Carter, campaigning for reelection in Michigan and Ohio before returning here to prepare for Tuesday's debate with Republican Ronald Reagan, told reporters he did not know when the hostages would come home. Carter has repeatedly warned that soaring expectations of imminent release might be disappointed.

Secretary of State Edmund S. Muskie, interviewed by a reporter while attending a football game at Duke University, where his son Ned is a freshman, said, "We have no contacts, we have no signal . . . we have no message" from Iran indicating that the hostages may soon be freed. "It's wrong to raise expectations," he added.

Ambassador to the United Nations Donald F. McHenry, however, was quoted by United Press International as having said to a reporter following an address in Cleveland Friday night that "I think it's likely the hostages will be released soon . . . not because any agreements have been reached yet, but because Iran has moved to the point where they're ready."

A spokesman for McHenry said the U.N. ambassador had been expressing his personal opinion rather than an official assessment.

State Department officials at high levels, especially those dealing with Iran, were in their offices yesterday monitoring the latest word from Tehran. iDespite the presence of a number of diplomatic intermediaries in the Iranian capital, officials here said they were receiving little that goes beyond the press interviews being given by various Iranian parliamentarians and other spokesmen.

The belief here was that Ayatollah Ruhollah Khomeini, who has the last word about nearly everything in Iran, has told the Majlis to reach a conclusion in its session today. The speaker of the Parliament, Hojatoleslam Ali Akbar Hashemi Rafsanjani, has said he expects the issue to be decided in one day's meeting.

The reflected sense in Washington of imminent decision has created a greater degree of anticipation about the hostages than at any time since last spring, when a United Nations commission failed to obtain release or transfer to the Americans. U.S. officials said later that the U.N. commission had gone to Tehran only after clear-cut commitments from President Abol Hassan Bani-Sadr to a scenario leading to the hostages' release.

The baleful history of last spring's disappointed hopes, which generated an atmosphere of bitterness and anger that led to the ill-fated U.S. rescue mission in late April, was in the minds and on the tongues of high officials who cautioned against excessive optimism now. From all appearances the United States had far greater assurances last spring than it has now. But on the other hand, some of the most powerful elements that blocked the release six months ago now appear to believe that holding the hostages is no longer in Iran's interest.

Some family members of the hostages, while steeling themselves against soaring hopes, are displaying signs of the suspense that has spread through official Washington. Mrs. Moorhead Kennedy, a leader of the group representing the families, said that "some of us were thinking of getting up every hour on the hour" last night to check the news, because the Iranian parliamentary meeting began early this morning.