President Carter welcomed Iran's decision yesterday to release the women and blacks among the hostages at the U.S. Embassy in Tehran, but the United States also made clear it will not consider the test of wills satisfactorily resolved until all the prisoners have been set free.

U.S. officials, operating under tight secrecy, were engaged last night in a variety of direct and indirect contacts with Iranian authorities to work out details for getting the dozen hostages to be released safely out of Iran.

Although the officials would say only that they have a "rough time frame" for the hostages' departure, it is expected that, barring unexpected complications, they will be released some time today.

The hostages likely will be flown by Iranian transport to a neighboring country, probably Turkey, and be transferred to a U.S. military plane. They then will be brought either directly to a U.S. military hospital in West Germany for temporary rest and any medical attention that might be required.

In the meantime, U.S. officials, saying their priority is getting the release successfully completed, refused to say anything about the implications of this latest development on the longer-range prospects of resolving the two-week-old crisis between Iran and the United States.

The tug of war began Nov. 4 when militant Iranian students, responding to agitation by Iran's defacto ruler, Ayatollah Ruhollah Khomeini, invaded the embassy compound and took those inside hostage to their demands that the United States return deposed Shah Mohammad Reza Pahlavi to Iran to stand trial as a criminal.

The United States' public response to the latest Iranian move was guarded. A White House statement, released on behalf of Carter, who is at Camp David, said:

"We welcome this announcement that some of the Americans held in the embassy in Tehran will be released. We are thankful the ordeal may be over for them and that they soom may be reunited with their families.

"We strongly urge that the authorities in Iran now move to secure the safe release of all those still being held. Their ordeal is not over. The United States government will continue to work in every channel open to it to achieve that end."

Later, however, White House press secretary Jody Powell pointedly reminded reporters that even if the women and blacks are released, roughly 58 hostages -- 50 of them Americans -- will remain.

"It's very important that no one loses sight of the fact we still have hostages illegally held in violation of the fundamental principles of international law, and we continue to hold those in authority in Iran responsible for the safety and release of the rest," Powell said.

Rosalynn Carter carried the same message to Florida, where she is pinch-hitting for the president at the state Democratic convention.

"We of course welcome the announcement that some of the hostages will be released," Mrs Carter told cheering delegates in St. Petersburg, "but we cannot forget that other hostags are still being held. Our goal must be the safe release of every single one of them."

Administration officials refused, publicly or privately, to speculate about the meaning of Khomeini's order to free the women and blacks. But his move hinted that the U.S. strategy may be working, slowly forcing Iran toward an accommodation that will see the hostages released without bloodshed.

The strategy has had three essential elements: trying to outwait the Iranians by avoiding provocative U.S. retaliations, firmly rejecting the demand for the shah's return and isolating Iran in terms of world opinion by keeping the dispute focused on the illegal nature of Iran's actions.

In addition, the United States has been trying to find a combination of steps that can be offered to Iran as concessions that will not violate American principles but that might open a face-saving way for the Iranians to back away from a showdown.

U.S. officials have said that effort initially was hindered by such political chaos within Iran that Washington was unable to identify those with authority to speak for Khomeini and the ruling Islamic Revolutionary Council and open channels for communicating with them.

Lalst week, however, U.S. officials here finally became convinced that they have an authoritative link to Khomeini through acting foreign ministry chief Abol Hassan Bani-Sadr. Since then, Washington has been paying special attention to Bani-Sadr's statements and using its communication channels to try to respond to them with suggestions for easing tensions.

These have included making clear to Tehran that a release of the hostages will mean a U.S. green light for a U.N. Security Council meeting sought by Iran to air its grievances against the shah and the United States. sWashington also unmistakably has telegraphed that the shah, who is in New York being treated for cancer, might soon be able to leave the United States for another country.

U.S. officials also have said they have "other options to throw into the mix," although they have been reluctant to say what might be involved. U.S. mofficials insisted last night they could not gauge with any accuracy the effect that the circuitious exchanges of the past few days may have had in bringing about the impending release of some of the hostages.

Some sources said the probing process had given Washington "some hints and indications" in recent days that the Iranian move was coming. But, as one source stressed, "We didn't really have a firm confirmation any sooner than the press or the rest of the world, which got the word yesterday morning from Radio Tehran."

The sources said one sign of possibly greater flexibility on the Iranian side was evident in the way Iranian authorities immediately began using the channels between the two capitals to get the process of releasing the hostages under way. But except for vague references to a "combination of some direct contact and some use of third-party intermediaries," the sources refused to specify how details for the release were being worked out.

The sources insisted that it still is too early to say what might happen next. Khomeini's move, they noted, might be a sign that he recognizes the United States will not back down and is seeking a way out of the impasse. Or it might be a ploy to break Iran's isolation and win support in Third World counries through a gesture involving women and blacks.

U.S. officials were unequivocal in making clear that they wanted any hostages who are offered release to accept. They said every effort was being made to communicate to the prisoners that the president wants everyone who can to get out -- that, as one source put it, "We don't want anyone volunteering to be a hero."