Ayatollah Khomeini, Iran's only undisputed leader, passed up a chance to guide parliament on release of the American hostages yesterday, leaving their fate in the hands of the assembly and increasing the likelihood of more delay.

Khomeini's silence on the hostages, in a speech to parliament members marking a Shiite Moslem holiday, was seen as an indication that the 80-year-old imam is reluctant to commit his influence and prestige until a public consensus develops among the legislatures. It was a disappointment to some Western diplomats in Tehran, who had hoped that the Iranian leader would offer advice on how to resolve the long-stalled hostage issue.

The parliament, or Majlis, took the day off after two days of inconclusive closed-door deliberations because of the Eid Ghadir feast, commemorating a declaration by the Prophet Mohammed that Shiites believe designated Ali as his successor. The assembly was scheduled to resume Wedensday its attempt to set conditions for release of the 52 hostages, held since the U.S. Embassy in Tehran was occupied Nov. 4, 1979, by Islamic militants.

In the first two days of debate, parlimentary sources told Reuter, controversy centered on suggested additions to the four conditions laid down by Khomeini: return of the late shah's fortune to Iran, unfreezing of Iranian assets in U.S. banks, withdrawal of legal claims on the assets and a promise not to interfere in Iranian affairs.

Among the proposed additions, which never got far enough for a vote, were demands that Washington pull its naval forces out of the Persian Gulf area and that the U.S. government formally apologize for past U.S. misdeeds in Iran, the sources said. Moreover, a minority bloc of fundamentalists was reported to be urging that consideration of the hostages be put off altogether until after the war with Iraq, or at least until after the U.S. elections.

Washington Post correspondent Ronald Koven reported from Paris that, in the assessment of European intermediaries in contact with officials in Tehran, the split in parliament also stems in part from divisions reappearing within the revolutionary leadership under Khomeini.

Unity in the face of the Iraqi invasion has begun to fade as parliament members grapple with the emotional and highly symbolic hostage issue, the intermediary sources said. This is particularly true of the rivalry between Ayatollah Mohammed Beheshti, generally recognized as head of the dominant Islanic Republican Party, and Hojatoleslam Ali Akbar Hashemi Rafsanjani, the parliament speaker, they added.

In addition, many Majlis members, particularly Islamic hard-liners and clergymen from rural areas, consider the hostage issue secondary to the war with Iraq and are oblivious to its effect on the impending U.S. elections, the sources said.

Khomeini, who has ordered the Majlis to set the final release conditions, seemed nevertheless to reflect some of these sentiments. In an hour-long speech in a mosque next to his home in the northern Theran suburb of Jamaran, he carefully avoided mentioning the hostages but included a rhetorical swipe at President Carter.

Comparing Carter with Iran's President Abol Hassan Bani-Sadr, who has spent most of his time at the warfront in recent weeks, Khomeini said in his broadcast speech:

"In which wars has Mr. Carter gone to battlefronts? He is sitting in the White House causing people to fight and be killed."

Khomeini devoted most of his discourse to Islamic philosophy and insistence that Iran cannot make compromises to get a cease-fire in its five-week-old war with Iraq, which he said has committed crimes "without parallel in history."

Washington Post correspondent Stuart Auerback reported from Baghdad that Iraqi officials also appear to be girding for a long war, citing Khomeini's attitude and a feeling that time is on Iraq's side because of Iranian shortages of military equipment, fuel and consumer goods.

First Deputy Prime Minister Taha Yassin Ramadan has said Iraq is prepared to do battle for as long as two years.In an indication of this, members of the Popular Army, a young Iraqi militia group, have begun moving into captured territory and to the battlefronts, Iraqi officials said.

"Should the Iranian regime choose to extend the war, then let it be long," Foreign Minister Saadoun Hammadi said in an interview published yesterday in the English-language Baghdad Observer. "Iraq will fight regardless of time to secure its legitimate rights."

According to analysts in Baghdad, Iraq appears well stocked with civilian and military goods. As a result, it is better equipped to hold out in a long conflict, they add.

Their assessment, coupled with Khomeini's hard-line statements, provided an inauspicious background for a new mediation attempt that Arab diplomatic sources said is about to be launched by the non-aligned movement. A six-man mission -- including envoys from Algeria, India, Pakistan, Yugoslavia, Zambia and Cuba -- is preparing to visit Baghdad and Tehran within a week, they said.

Previous mediation attempts by President Mohammad Zia ul-Haq of Pakistan, current president of the 40-member Islamic Conference, have failed to move the two warring Moslem neighbors beyond uncompromising positions that in effect make peace negotiations impossible. Observers pointed out, however, that President Saddam Hussein of Iraq takes a particular interest in the 94-member nonaligned movement and is to take over as its next chairman at a summit scheduled for Baghdad in October 1982.

"If anyone can persuade the antagonists to cease fire, it is the non-aligned movement," an Arab diplomat in Baghdad told Reuter. "At least in Baghdad, it has more pull than anyone else."

The Iraqi High Command reported, meanwhile, that Iran's U.S.-made F4 Phantom fighter-bombers raided the northern Iraqi cities of Kirkuk and Mosul, resulting in the downing of an Iranian jet in a dog-fight with a Soviet-made Iraqi Mig.

The two cities lie in Iraq's main oil fields, from which pipelines carry crude west toward the Mediterranean and refined products south to Baghdad. But European sources working in the region say the refinery at Kirkuk has suffered little damage despite repeated bombing raids by Iranian warplanes.

In the main battlefields at the head of the Persian Gulf, the Iraqi Baath Party newspaper Al Thawra claimed that Iraqi soldiers are trying to clear the debris left by a month of artillery bombardment in an effort to allow a return to a semblance of normal life in Khorramshahr.

The key Iranian port city, on the disputed Shatt-al-Arab waterway, was claimed by Iraq Friday. Iranian radio broadcasts insist, however, that some Revolutionary Guard defenders are still holding out. The official radio said yesterday that Revolutionary Guards assisted by naval commandos, police and militiamen have prevented Iraqi forces from crossing the Karun River bridge in one corner of the city, blocking a key access route to Abadan 10 miles to the south.

Iraqi authorities have barred foreign correspondents from traveling from Baghdad to Khorramshahr to verify the conflicting claims.