President Carter met with the Joint Chiefs of Staff at Camp David yesterday amid heightned concern in the administration over what a coming week of religious fervor in the Moslem world will mean for the 49 Americans who remain hostages inside the U.S. Embassy in Tehran.

Carter's three-hour meeting with the military chiefs at the presidential retreat in the Maryland mountains centered on the defense budget, White House press secretary Jody Powell said. If Iran came up during the meeting, it was not a major topic of discussion, he added.

Publicly, neither the president nor other top administration officials had anything to say yesterday about the embassy takeover or the latest pronouncements of Iran's revolutionary leader, Ayatollah Ruhollah Kohmeini.

In a speech broadcast on Iran's state radio, Khomeini accused Carter of violating "all human rights" and called on Moslems to rise up against the United States and "its stooge, Israel," which he once again accused of plotting the takeover of the Great Mosque of Mecca.

Privately, there were continued indications that administration officials expect the standoff with Iranian authorities, which yesterday entered its 21st day, to continue into next month.

"I don't see anything likely to produce a breakthrough," one official said.

Adding to the conern of the White House is the timing of the Moslem holy period of Muharram, which will reach its climax next weekend. It is a time traditionally marked by mass exuberance and even violence which, when coupled with the anti-Americanism Khomeini has sought to stir in Iran and elsewhere in the Moslem world, could heighten the dangers to the American hostages, administration officials fear.

It was this concern that prompted the president's warning Friday that the Iranian government would face "extremely grave" consequences if a single hostage were harmed.

The danger, U.S. officials see it, is that a combination of religious frenzy and anti-Americanism could lead to uncontrollable violence directed at the hostages. Iranian authorities would be under strong pressure to let such an outburst run its course.

Carter's message Friday was meant as a warning that the United States would consider the Iranian government fully responsible for harm done to any of the hostages, officials said.

The end of Muharram is also likely to coincide closely with what could be another important element in the Iranian crisis -- the departure from the United States of deposed Shah Mohammad Reza Pahlavi, who is undergoing treatment for cancer in New York.

The shah, whose return to Iran to stand trial on criminal charges is being demanded as the price for freeing the hostages, has said he expects to leave the United States in the next week or two.

In the meantime, administration officials suggested yesterday that U.S. spokesmen will refrain from public comment except in the event of new developments or statements from Khomeini indicating possible "miscalculations" of American intentions.

It was in keeping with this strategy that the president last Tuesday warned of military retaliation if the hostages were harmed. The White House issued the warning after Khomeini declared in a speech that the hostages might be tried as spies and that Carter was afraid to resort to military force.

However, U.S. officials stressed yesterday that the administration is not ruling out military action under circumstances less drastic than the killing of some or all of the hostages. The range of sufficiently provocative acts could include the prosecution of the hostages on espionage charges, for example.

In addition to the chiefs of the military services, those who met with the president yesterday included Defense Secretary Harold Brown, Deputy Defense Secretary W. Graham Claytor and national security affairs adviser Zbigniew Brzezinski. The administration has promised to give the Senate a preview of the next fiscal year's defense budget and plans for military spending over the next five years before debate begins on the strategic arms limitation treaty with the Soviet Union.

Elsewhere in the administration, there was a lull in the preoccupation with Iran. Yesterday, for the first time since Nov. 5, the day after the embassy takeover, there was no briefing at the State Department on the Iranian situation.

Carter, who had planned to spend last week vacationing on Sapelo Island, Ga., but instead went to Camp David, is scheduled to return to the White House late this afternoon. Powell said the president is not expected to have any public comment on Iran.