The White House, facing increasing skepticism about its hopes for a break in the Iranian crisis, refused yesterday to divulge the contents of a new note the United States has sent to Tehran, but insisted it still believes that the Iranian government intends to take custody of the American hostages in the U.S. Embassy there.

Press secretary Jody Powell, responding to reports that Iranian President Abol Hassan Bani-Sadr was dissatisfied with President Carter's original reply to Iranian demands turned aside questions about the reported new message by saying "I'm not going to get into discussions about the traffic back and forth." However, officials confirmed that a "government-to-government" message had been sent to Tehran.

Powell said that the administration is getting "conflicting signals" from Tehran and is still trying to obtain "adequate clarification" about what the Iranians want.

U.S. officials, who asked not to be identified, elaborated by saying that Carter wants to be cooperative in helping Bani-Sadr's efforts to outflank the hostages' militant captors. But, the officials added, there are limits to how far Carter can go in acceding to Iranian demands that, if taken literally, could mean an idefinite moratorium on U.S. statements about the plight of the hostages.

Powell said U.S. officials believe the confused situation in Tehran and the continuing delays in getting the hostages transferred reflect an ongoing power struggle among the various factions there. But, he insisted, it is too early to conclude that the latest effort to break the 5-month-old impasse has failed.

In the meantime, he said "we intend to continue to be restrained in our words and actions so long as real progress is made in resolving this crisis and bringing our people home."

While repeating Carter's warning Tuesday that there are limits to U.S. patience, Powell refused to say how long the U.S. restraint will continue or whether the president plans to set any new deadlines for action by the Iranians.

Instead, Powell said: "Our expectation is that the Iranian authorities will do what they said they will do -- that is, take custody of the hostages. If at some point we're forced to conclude that is not the case, we'll have to deal with that situation. But we haven't reached that point."

The administration's move into this holding pattern came as the continuing lack of action on the hostage transfer, originally expected early Monday, caused growing speculation that Carter once again had been misled by Iranian promises or had manipulated the American public's hopes for progress to help him with Tuesday's Democratic presidential primaries in Wisconsin and Kansas.

However, these suspicions were heatedly denied by administration officials, who continued to insist that Carter has private assurances about the intentions of Iranian authorities. These assurances, White House sources said, were sufficient to convince the president that there were reasonable grounds for optimism on the hostage issue and to prompt him to defer the economic and political sanctions he had threatened to impose against Iran under a deadline originally set for Monday.

Although this tone of continuing cautious optimism was evident in all the administration's public statements yesterday, some sources, notably within the State Department, privately sounded increasingly pessimistic about the outlook for the latest initiative.

These sources, while refusing to be specific about the nature of the Iranian assurances, said they were not strong enough to justify the full-throttle display of optimism staged by the White House on Monday. However, these sources, while saying in retrospect that it might have been wiser for the United States to have responded in a more cautious fashion, added that the situation, if not grounds for "raving optimism," was still too unclear to make any predictions about the outcome.

The latest hitches in the maneuvering between Washington and Tehran were caused by reports Tuesday night that Bani-Sadr had characterized Carter's statement earlier in the day, deferring the U.S. sanctions, as failing to meet Iranian demands that the United States refrain from any "provocation or propaganda" against Iran.

A report from Washington Post correspondent Jonathan C. Randal in Tehran said the new U.S. message, delivered yesterday, did no more than repeat past U.S. assertions that the hostages should be freed as soon as possible and note Iran's intention to have their fate decided by the new Iranian parliament.

According to the report from Randal, Bani-Sadr, in disclosing the latest U.S. message, referred to it in an approving manner -- thereby hinting that the Iranians might be backing away from their call Tuesday for Carter to formally renounce any sanctions or criticsm as the price for the hostages' transfer.

Powell, citing the difficulty in ascertaining the Iranian government's "attitude or intentions at the moment," said that since Tuesday night he had seen three different and conflicting press accounts of what the Iranians want. The United States, he said, has "no substantiation" for any of them, and he added: "I have no idea on this earth what those reports reflect."

But he insisted: "The bottom line is it's our view that this thing will work out and that the Iranian authorities will do what they've said they will do, even though there may be a lot of confusion in the process."