Among Carter administration officials, last week's abrupt suspension of a United Nations commission's inquiry in Iran evoked what one called "the kind of enthusiasm with which you'd contemplate radical surgery."

Two weeks earlier, when the commission first went to Tehran, there had been guarded but unmistakable optimism in administration ranks that a mechanism finally had been found for resolving the four-month crisis over the 50 American hostages in the U.S. Embassy there.

Instead, the most recent bitter surprise from Tehran has left President Carter with no option other than clinging to hope that the commission eventually can be put back on the track toward a solution.

Meanwhile, there have been rumblings about whether the U.N. commission -- the maneuver on which Carter has staked most of his chips -- was an ill-conceived idea that only enabled Iran's radical leaders to further humiliate the United States.

That assessment isn't shared by other governments that has criticized many of Carter's moves in foreign policy. Almost without exception, they seem to agree that the United States, confronted in Iran by adversaries unwillingly or unable to play by any of the accepted rules of diplomacy, has no choice other than to pursue patiently every avenue that offers even the slightest hope of a negotiated settlement.

The United States found its original single goal in Iran -- freeing the hostages -- complicated by the Soviet invasion of Afghanistan. That transformed what had been a test of wills between Washington and Iran's revolutionary zealots into part of a large U.S.-Soviet competition for influence in the Pursian Gulf, with its vital oil supplies.

For that reason, the administration, beginning in January, backed away from its original tough posture of economic pressure and veiled threats of possible military action and adopted a more conciliatory approach. It was encouraged by the overwhelming election of Abol Hassan Bani-Sadr, a moderate on the hostage issue, as Iran's president.

The hope ws that Bani-Sadr would be able to surmount the feuding of Iran's fractured internal power structure and gain the backing of its most influential figure, Ayatollah Ruhollah Khomeini, for a showdown with the militants holding the hostages.

In agreeing to appointment of the U.N. commission, the United States thought it had the best available device for enabling Bani-Sadr to satisfy the emotional Iranian demand for redress of its grievances against deposed shah Mohammad Reza Pahlavi and the United States.

The commission's mandate has not been spelled out publicly. But U.S. and U.N. sources have made clear that it involved a specific "package deal" understood and agreed to by all parties, including Iran.

Its two-pronged purpose was to hear Iran's grievances and to pave the way for release of the hostages through a series of "reciprocal steps."

Publication of the commission's findings was contingent on Iran carrying out its promise to permit the commission to see each of the 50 hostages and to transfer them from the control of the militant captors to Iran's Revolutionary Council.

With the captives under control of a government authority, the way would have been prepared for a further and theoretically final step -- satisfaction of Bani-Sadr's demand that the United States acknowledge its past actions in Iranian affairs or impede attempts to have the shah extradited.

However, last weekend, even at Carter privately was signaling his willingness to try to comply with these demands, the Iranian end of the deal collapsed. The militants, supported by extremists of the right and left, refused to surrender the hostages or let the commission see them, and when the dispute was referred to Khomeini, he backed the militants.

U.S. officials, shocked by the sudden turnabout, initially talked about the inevitability of returning to tougher measures. But, after giving the matter more thought, the administration is known to have concluded that Bani-Sadr and his moderate allies of the Revolutionary Council had not intentionally "suckered" the United States, as some Carter critics charged.

Instead, according to the U.S. analysis, he simply hadn't solidified his power base sufficiently to have the clout to carry out his end of the bargain. But, U.S. officials believe, if the balloting now under way for an Iranian parliment produces a majority in accord with Bani-Sadr, he could be in a position to confront the militants more successfully in another month or two.

For that reason, Carter clearly has decided on a strategy of avoiding, as much as possible, actions that could harm Bani-Sadr by increasing anti-American sentiment within Iran and of hoping that the coming weeks will shift the balance of power there to those who want the crisis ended.