President Carter said last night that creation of a United Nations commission to hear Iran's grievances could help resolve the Iranian crisis, but he refused "at this delicate time" to discuss the rising tide of rumors about an imminent deal to free the American hostages in Tehran.

Carter, appearing at his first news conference in 11 weeks, sought to cut off questions about the hostage situation with an opening statement in which he said there "recently have been some positive signs." But he added:

"I cannot afford at this delicate time to discuss or comment further upon my specific efforts that may be under way or any proposals that may be useful in ending this crisis."

Carter's comments came amid intense speculation that recent statements by Iranian President Abol Hassan Bani-Sadr about an Iranian proposal on the hostages may have signaled the impending end of the lengthy crisis.

But, although U.S. officials are known to be hopeful about the still-secret Iranian plan, they also warned in advance of Carter's news conference that considerable, behind-the-scenes negotiation is still required and that the American public should not expect any sudden or dramatic developments.

There is general agreement that any solution would include, as one element, creation of an international commission under U.N. auspices to hear Iranian complaints against deposed Shah Mohammad Reza Pahlavi. Since the early days of the crisis, the United States has signaled repeatedly that it would agree to such a commission provided its creation is tied to release of the captives.

In his statement last night, Carter did little more than acknowledge publicly this U.S. position. He said:

"Since mid-November we and the Iranian officials have been discussing with Secretary General [Kurt] Waldheim of the United Nations his proposal to send a commission of inquiry to Tehran. We would support steps by the United Nations that would lead to release of the hostages if the steps are consistent with our goals and our essential international principles.

"An appropriate commission with a carefully defined purpose would be a step toward resolution of this crisis."

Although his opening statement effectively blocked further questioning about the Iran situation, Carter had these comments about other aspects of the crises the United States is grappling with in Southwest Asia:

He reiterated in especially harsh language his condemnation of the Soviet Union for its Dec. 27 invasion of Afghanistan, saying the United States cannot let the Soviets "choose the terrain or tactics" for superpower confrontations and asserting the need to demonstrate "through peaceful needs" that Moscow cannot invade other countries with impunity.

He underscored that Feb. 20 remains the deadline for the Soviets to pull out of Afghanistan if they want to avoid U.S. efforts to boyscott or otherwise hamper the Olympic Games in Moscow this summer. Asked if he might lift U.S. opposition to the Moscow Games if the Soviets withdraw by May. Carter replied: "I don't see any posibility of that."

He said he generally was "well pleased" with the support and cooperation the United States has received from its major allies in dealing with the Afghanistan situation. While conceding there have been differences such as the recent refusal of France to attend a foreign ministers' meeting in Bonn to discuss Afghanistan, Carter said that such incidents reflected only "nuances of differences" and did not detract from basic allied cooperation.

He said there has been a "gross overreaction" to his call for registration for the draft, emphasizing that he does not plan to call for military conscription. "The best way to avoid adraft and mobilization in the future is to be prepared," he said in defense of the registration plan.

In reference to talk that the Soviets might put pressure on Yugoslavia, Carter said the Yugoslav government had made clear its ability to defend itself. If Yugoslvia does ask for help, he added, the United States and its European allies "would seriously consider it."

Carter's ranging over these various points left unanswered, though, the questions that had generated such interest in his press conference -- those relating to the future of the 53 Americans in the U.S. embassy compound and Iranian foreign ministry in Tehran.

Since the election two weeks ago of Bani-Sadr, and 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 had been held out to Iran through the United Nations.

In broad outline, it calls for establishment of an international commission to investigate Iran's grievances in exchange for release of the hostages. The proposal also contains several possible ideas for keeping the hostages in custody of a third party while the commission does its work and for the timing of the hostages' release and the publication of the commission's findings.

On Monday, Bani-Sadr, in an interview with a French newspaper, said Iran had a plan of resolving the hostage issue without a U.S. commitment to hand over the shah. Yesterday Bani-Sadr added that the plan, whose details he would not disclose, had been approved by Ayatollah Ruhollah Khomeini, who hold ultimate authority in Iran.

The Iranian statements touched off what a State Department official on Tuesday called "a thousand rumors" that the two countries were on the verge of breaking the impasse and reaching an accord that would free the hostages.

However, Carter administration sources have been warning since Monday that they did not expect the Iranian plan to be anything more than the start of a negotiating process that could still take considerable time.

The United States, the sources have said, expected the Iranian proposal to contain demands unacceptable to Carter. However, they added, there is optimism within the administration that the Iranian plan will offer sufficient common ground to allow talks to proceed under the mediation of Waldheim or some other third party.

As of last night, the administration was still keeping a blackout on details of the Iranian proposal, and U.S. officials would say nothing beyond characterizing news reports purporting to give these details as "incorrect."

Administration sources acknowledged that creation of an international commission was, as one put it, "obviously a central part of any possible solution." Other than that, though, the sources said only that a number of factors require clarification or sorting out before the administration will know whether there are grounds for real optimism.

Some sources, noting a flurry of contradictory statements coming from Iranian officials, hinted there was some confusion within the administration about the precise nature of the Iranian plan. As of last night, these sources said, there was not even complete certainty here about what Khomeini had approved.

On hint of a possible stumbling block in the Iranian plan has been Bani-Sadr's frequent statements that the United States must admit its guilt for helping subjugate Iran to the shah, and it must permit the current Iranian government to pursue its efforts to get back the shah and his wealth.

U.S. officials have said the United States has no intention of making any admission of guilt. When Carter was asked last night about covert U.S. backing for the 1953 coup that solidified the shah's control over Iran, he responeded:

"That's ancient history. I don't think it would be appropriate to go into the propriety of something that happend almost 30 years ago."

Other protential problems involve the U.S. position that any commission should not have the power to order or even call for the shah's extridition, and U.S. insistence that release of the hostages must, at the very minimum, take place simultaneously with the public release of the commission's findings. t

Although Carter did not address these point directly, he seemed to be reaffirming that the United States will not back down on these conditions. That appeared to be implicit in his carefully worded reference to U.S. support for U.N. efforts "if the steps are consistent with our goals and our essential international principles" and "an appropriate commission with a carefully defined purpose."