President Carter is expected to reveal at a news conference tonight whether he sees any hope for an imminent break in the 102-day hostage crisis, U.S. sources said yesterday.

Announcement of the news conference came amid rumors of a possible deal to free the Americans.

Except for saying that Carter will appear before the press at 8 p.m. EST and probably will make an unspecified opening statement, the administration clamped a lid on all public statements about the Iranian situation.

But some sources acknowledged that an Iranian proposal for dealing with the hostage issue has been under intensive study within the administration for two days.They added that they expect Carter to give his response on the Iranian plan tonight.

According to the sources, the scheduling of the news conference in the face of what a State Department spokesman called "a thousand rumors" is an indication that Carter now is willing to be questioned publicly about the Iranian crisis.

Earlier yesterday, administration sources had said he would not put himself in that position until the administration had completed its analysis of the Iranian proposal and had an indication of whether it has the approval of Ayatollah Rohollah Khomeini, Iran's ranking authority.

However, the sources cautioned, even if Carter said his top advisers decide that the Iranian plan offered a basis for negotiating over the hostages, there is not much expectation within the administration of a sudden and dramatic turn that would see the captives freed within a few days.

Instead, the sources said, the administration seems to be hoping at best for the start of a negotiating process that could take weeks to complete.

Fueling the rumors of a potential breakthrough was an interview with Iranian President Abol Hassan Bani-Sadr published Monday in the French newspaper Le Monde. In it, Bani-Sadr said Iran's Revolutionary Council had asked Khomeini to approve a plan that would free the hostages without a U.S. commitment to hand over deposed shah Mohammed Reza Pahlavi.

Although Bani-Sadr gave only the sketchiest details of the plan, he said it would require the United States to make "a self-criticism . . . of the crimes it committed in Iran for a quarter-century" and to recognize Iran's right to extradite the shah and regain the fortune he allegedly took out of the country.

On Monday, State Department spokesman Hodding Carter said the United States had no intention of "declaring its guilt, either specified or unspecified."

In response to further questions yesterday, the spokesman said: "Official comment by the administration on each proposal, suggestion or rumor that may be raised in general or specific terms from a variety of sources is neither necessary nor productive. Therefore today I will have no further comments on the hostage situation or any of the various stories about it."

Since the election two weeks ago of Bani-Sadr, an outspoken moderate on the hostage issue, U.S. officials have been hopeful that he would move in the direction of negotiations along the lines of a "package deal" plan that has been held out to Iran through the United Nations and other intermediaries.

In broad outline, the package plan, which has several possible variations, calls for establishment of an international commission to investigate Iran's grievances against the shah and the United States in exchange for release of the hostages.

To get around the sensitive problem of timing, the plan includes tentative suggestions for the hostages to be put in the custody of a body such as the International Red Cross or sent to a neutral country such as Algeria while the commission makes its inquiries. Then, release of the captives and the public revelation of the commission's findings would take place more or less simultaneously.

U.S. officials are known to have expected any Iranian counterproposal to contain demands the United States cannot accept. However, the hope has been that the Iranian plan will offer sufficient common ground to make a start on further negotiations.

These negotiations, if they are launched, are expected to be conducted through third-party intermediaries. Although there are several possibilities about who might fill that role, most speculation has centered on U.N. Secretary General Kurt Waldheim.

In addition to assessing whether the Iranian plan provides a basis for talks, U.S. officials also are known to believe that there can be no successful outcome unless Bani-Sadr has Khomeini's backing.That is considered essential to forcing the Iranian militants holding the hostages to cooperate with any peaceful solution.

What was not known last night were the conclusions that President Carter has reached about these points, and these are expected to be made clearer at his news conference tonight.