Carter administration officials, pausing yesterday for a brief Thanksgiving lull in the Iranian crisis, reiterated the determination of the United States that all of the American hostages in Tehran be freed safely.

The tone was set by Secretary of State Cyrus R. Vance when he went to Andrews Air Force Base to welcome the 13 black and women hostages released by the Iranians earlier this week. Referring to the 49 Americans still being held in Tehran, Vance said:

"Let me assure you we will not rest or relent in our efforts until every one of your colleagues stands safely on American soil. We will continue to pursue every avenue available to us until all of our people are home. We will continue to stand firm. We will continue to stand as a nation united."

At the State Department, spokesman Hodding Carter, asked about reports of possible compromises being discussed behind the scenes, insisted that release of the hostages is a precondition to talks about any other aspects of the tensions in U.S.-Iranian relations.

That has been the U.S. stance since the beginning of the crisis Nov. 4 when militant Iranian students, egged on by Iran's de facto ruler, Ayatollah Ruhollah Khomeini, stormed the embassy in Tehran and took the hostages. The militants since have been demanding that the deposed Shah Mohammad Reza Pahlavi be returned to Iran as a criminal. He is being treated for cancer and gallstones in New York.

This week the administration toughened its position, first by suggesting that the United States might use military force against Iran and then, in the wake of Wednesday's attack by moslem mobs against the U.S. embassy in Pakistan, by escalating official criticism of Khomeini for allegedly trying to incite anti-American violence in the Persian Gulf area.

Privately, U.S. sources say this pressure is aimed at keeping Iran isolated in world opinion and forcing it to move toward a diplomatic solution of the impass. Although the outlines of such a solution are still unclear, its potential main elements are understood to be under discussion at the United Nations and in other diplomatic channels.

Specifically, they would include the release of the hostages followed by a U.N. Security Council debate at which Iran could air its grievances against the United States and the appointment of an international commission under U.N. auspices to investigate the shah's "crimes." As a further means of defusing tensions, the shah almost certainly will leave the United States, probably late next week when his current course of treatment is completed.

But, while U.S. sources privately concede that all these ideas have been floated, they also insist that release of the hostages is a precondition that must be met before the United States will agree to any other elements of the package.

In addition, the sources say, Washington still has no really clear idea of whether such a deal would be acceptable to Khomeini. Although several Iranian government officials and outsiders claiming to speak for Iran have touted different parts of the package publicly, the administration is convinced that Khomeini alone can make the decision, and it is unclear to what degree any third parties are authorized to speak for him.

In regard to another aspect of the Persian Gulf situation Hodding Carter went to special lengths yesterday to stress that the United States was fully satisfied with the attitude and cooperation of Pakistan President Mohammad Zia ul-Haq's government in rescuing the Americans who came under attack at the embassy in Islamabad Wednesday.

Reports from Islamabad quoted several Americans as saying they were under siege and in grave danger for several hours before Pakistani troops arrived and led them to safety. In the interim, four persons inside the embassy compound, two Americans and two Pakistani employes, were killed.

Hodding Carter said "the adequacy and efficiency" of the Pakistani response was a question that is being looked into by both the United States and the Zia government. But, he stressed, there was no doubt about the willingness of Pakistani officials "up to the highest levels" to protect the Americans.

The spokesman also said the United States was trying to investigate reports that the Islamabad attack had been triggered by a radio broadcast charging U.S. complicity in an attack against the Great Mosque in Mecca and that the mob action was under some kind of orchestrated control. So far though, he added, the U.S. probing had failed to turn up any illuminating evidence of what happened.

In one of the first indications that the cutoff of U.S. oil imports from Iran will have an impact here, Ashland Oil Inc., one of the biggest purchasers of Iranian crude, has asked the Energy Department to consider special allocations to help the company make up an estimated 100,000-barrel-a-day crude oil shortage.