Fearing that Ayatollah Ruhollah Khomeini may succeed in squeezing Iranian Prime Minister Shahpour Bakhtiar from office within a day or two, the State Department declined yesterday to associate itself actively with Bakhtiar's fate.

Reports reaching Washington from Tehran that Khomeini's forces are pushing to get the parliament to meet this week and refuse to give Bakhtiar a vote of confidence have reportedly caused U.S. policy-makers to revise downward their estimates of Bakhtiar's chances for survival.

But White House press secretary Jody Powell denied late yesterday that President Carter had concluded that Bakhtiar's government could not surmount the political challenges it faces.

Carter was told yesterday that Bakhtiar's government is in a better position now as a result of its handling of Khomeini's return last week and because of new cohesiveness in the army, a senior U.S. official said.

That assessment was given to Carter and his top foreign policy advisers yesterday by Gen. Robert Huyser, who has been in Iran for the past month consulting with Iran's military commanders. Huyser flew back to Washington Sunday, U.S. officials disclosed.

The administration's decision to pull Huyser out of Iran now was spurred in part because of the growing controversy around the general's role, U.S. officials said. Huyser has been denounced in Iranian street demonstrations as a "vice regent" and portrayed by Khomeini followers as leading an American plot to keep Bakhtiar in power.

President Carter and some aides have reportedly suggested in recent comments that they put greater reliance on Huyser's assessments than on the more pessimistic political reporting of the U.S. embassy in Tehran.

Administration spokesmen have publicly said that Huyser, deputy commander of U.S. forces in Europe, has been in Iran to urge the military not to stage a coup against Bakhtiar, and to try to make sure that the military did not split apart.

The sudden twists and turns of the Iranian political situation in recent days have left the Carter administration clinging to the Carter administration clinging to the army and to the often amended, often ignored, constitution of 1906 as the only two levers of policy still available in the crisis.

Some senior administration officials have concluded that the best the United States can hope for at this point is a new coalition government in which Bakhtiar will participate or to which he will give his blessing.

The Iranian constitution is sufficiently vague for any number of facesaving solutions to emerge if both Bakhtiar and Khomeini opt for coexistence, these officials feel.

Bakhtiar was appointed prime minister by the shah just before the Iranian monarch left the country, perhaps forever, last month. In the administration's view, Bakhtiar has become the symbol of continuity and constitutionality that the Iranian army is said to insist on maintaining.

The reported move by Khomeini's forces to have a vote in parliament that would force Bakhtiar's government out by legal means puts the United States in a policy dilemma, since the administration has repeatedly said it will accept any orderly and constitutional solution devised by the Iranian people.

At yesterday's daily briefing, State Department spokesman Tom Reston was repeatedly asked to state, or restate, the U.S. position on Iran in the wake of Khomeini's decision to name a "revolutionary prime minister."

Reston would say only "our position is unchanged." He refused to articulate the position, referring reporters to a Jan. 4 statement made before Bakhtiar was installed and the shah left Iran.

The administration continued to voice open support for Shah Mohammad Reza Pahlavi long after he had lost control of his country, and reportedly fears being burned again by being too closely identified with Bakhtiar in a political confrontation he may lose.

Moreover, policymakers doubt that an open statement of support would help Bakhtiar, whom Khomeini is portraying as an American agent.

Huyser briefed the president, national security affairs adviser Zbigniew Brzezinski, Secretary of State Cyrus R. Vance and Secretary of Defense Harold Brown. A U.S. official said that Huyser portrayed the Iranian army as "sticking together better" now and that the threat of its disintegration has receded.