The Carter administration has abandoned any hopes of restoring the shah of Iran to full power. It is instead emphasizing its support for a civilian government to succeed the shah as the country's effective authority, White House and State Department officials acknowledge.

These officials, who work actively on the Iranian crisis, do not state the administration's shift in policy focus in terms as stark as these. But in a series of interviews over the past week they have listed national priorities and American policy concerns in ways that clearly signal a major and traumatic shift in policy for the Carter administration.

That shift is certain to remain unarticulated by an administration that does not want to be seen at home and abroad to be undercutting a long and valued ally. The administration also genuinely wants to avoid appearing to be telling the Iranians that Washington knows better than they do, U.S. officials emphasize strongly.

But the changed assessment is becoming apparent in both the increasingly muddied pronouncements of State Department spokesmen, who now have to be drawn out by reporters before they will give the kind of statements of support for the shah that the department eagerly made on its own two months ago, and perhaps more importantly in the private deliberations of an Iranian task force at work at the State Department.

The deepening pessimism of many U.S. officials was reportedly reflected at a subcommittee meeting of the task force yesterday, in which Iran desk officer Henry Precht, the official who has most closely observed the crisis on a day-to-day basis, told the group that it now appears that "99 percent" of the Iranian people do not support the shah, according to reliable sources.

Precht said he did not remember making the remark at the meeting, and that if he had said those words, they were not intended as a serious assessment.

Moreover, a series of leaks in Washington and Tehran about diplomatic decisions over the past few days has served to air the administration's misgivings about the shah's future without forcing the White House to take the responsibility for doing so. President Carter has been in Guadeloupe for a four-power summit meeting and vacation.

Senior officials said yesterday that they would not be surprised to see the shah leave Iran by this weekend if the proposed civilian government of Prime Minister-designate Shahpour Bakhtiar can be put into place firmly so Iran can begin to return to normalcy after a year of upheaval.

These officials concede, however, that it still remains highly uncertain that Bakhtiar will be able to form a stable government.

Other U.S. analysts say that Bakhtiar's failure to persuade Gen. Feydoun Jam to become his defense minister has seriously weakened the civilian politician's bid for power, and may have torpedoed any plans by the shah to leave shortly with open U.S. blessings for that solution.

If asked, the U.S. ambassador to Tehran, William H. Sullivan, will emphasize to the shah American concern over an orderly transition and U.S. desires that a stable and functioning government be in place before the shah leaves Iran on what would be described as a vacation but what might be the end of his 37-year rule, a senior U.S. official said yesterday.

Policy deliberations in Washington have focused on continuity and an orderly flow of power from the shah to another governing authority, this official said, adding that the deliberations have not emphasized the question of whether Sullivan should advise the shah on leaving or staying in Iran.

Two senior officials in separate comments said that emphasis in the discussions have been on how the civilian government can be made more credible and the military encouraged to support it once the shah turns over power, and on what American relations with a post-shah government would be like.

Security surrounding communications has tightened in the wake of complaints from Ambassador Sullivan about leaks that suggest he is shifting from his previously identified position of total support for any course of action chosen by the shah to a more ambiguous stance, U.S. officials report.

Instructions are being relayed directly to Sullivan by Secretary of State Cyrus R. Vance on the telephone or direct Telex link, and are not being handled in regular diplomatic cables, according to a State Department official.

The Vance-Sullivan communication link has replaced the frequent policy telephone conversations that were held in November between President Carter's national security affairs adviser, Zbigniew Brzezinski, and the Iranian ambassador to Washington, Ardeshir Zahedi, now in Tehran to rally support for the shah.

The White House supported the shah's turn to the military to try to contain the year-long violent protests against his rule in clear terms, and in background sessions reporters were told that the shah would have unswerving support from the administration for whatever policies he chose.

The failure of the military to restore order and of the shah to act decivisely once that failure became clear seriously eroded Washington's confidence in his ability to survive, however.

As this erosion began, Brzezinski brought in George W. Ball, former under secretary of state in the Kennedy and Johnson administrations, to do a special study on U.S. policy options in the Persian Gulf.

Ball concluded that the military government would fail to restore order, and that the U.S. policy should be to encourage the shah to step aside in favor of a coalition civilian cabinet drawn from the opposition.

Senior officials now indicate that although no changes in policy were made as a result of the Ball report, the White House now recognizes that events have unfolded in the direction predicted by Ball, although at a slower pace than he suggested.

This recognition, an extremely painful one for Carter and Brzezinski, appears to have come home with full force in late December. But the White House evidently decided that, for a number of reasons, ranging from domestic political considerations to regional and global policy matters, it could never articulate the changed assessment.

The result has been an increasingly confused and muddied policy profile, with State Department spokesman Hodding Carter daily retreating an inch at a time by emphasizing American concern that the Iranian constitution be followed.

A turning point appears to have come Dec. 31 at a meeting of the Cabinet-level Security Coordinating Committee at the White House, where the focal point for shaping many of the American pronouncements and operational decisions on Iran was effectively shifted from the White House to the State Department, and particularly to the interagency task force headed by Undersecretary of State David D. Newsom.

In essence, officials acknowledge indirectly, other priorities simply overtook the White House's initial determination to continue repeating its support for the shah and to take no actions that would be seen to be undermining him.

In early December, Brzezinski's fear that the administration would be seen to lose confidence in the shah if it approved government payment for departure of U.S. military and diplomatic dependents in face of rising anti-Americanism, triggered a sharp debate and delay by the administration on that move.

By the end of the month, however, after an American oil executive was assassinated, there was no debate in Washington about Sullivan's decision to urge all dependents to leave, and to set up a ticketing operation inside the embassy compound. The increasing confusion around the public statement of U.S. policy appeared to some diplomatic observers to be buying time to get Americans out of Iran.

U.S. officials also report that Zahedi, who had strongly opposed the early December decision by Washington on dependents, raised no objections when the ticketing operation was begun inside the embassy.

Hodding Carter said yesterday that the number of Americans in Iran has dropped from an estimated 41,000 two months ago to 12,000. He estimated that 500 to 600 Americans a day had been leaving Iran, after the Dec. 31 decision by the administration to encourage and facilitate the exodus.

Nuances also crept increasingly into policy decisions and pronouncements as Vance, freed from direct involvement in Middle East and strategic arms talks, consulted directly with the president and became more involved in the Iran policy.