Iraq, announcing tonight it plans to initiate a unilateral, four-day cease-fire in its war against Iran, included conditional clauses and drew an immediate rejection from Iranian representatives here.

As a result, the proposal appeared to offer little hope of ending the conflict that began 10 days ago.

Iraq said the proposal was intended to permit "futher consultations" by Islamic countries seeking to mediate. The Iraqi spokesman had emphasized initially that Iranian accord was not required to implement the cease-fire, although "we will return the fire" should the Iranians initiate it after Sunday.

A conference of representatives of Isamic nations at the United Nations seized on the Iraqi move as a basis for asking Pakistani President Mohammad Zia ul-Haq to continue his "goodwill mission" aimed at persuading both sides to accept a border cease-fire.

That was generally interpreted here as a request for Zia, who earlier this week visited Baghdad and Tehran, to return for another attempt to halt the fighting.

Pakistani Foreign Minister Agha Shahi, who also is chairman of the Islamic conference here, cautioned that the method of pursuing the mission is up to Zia and that no decisions have been made about his next steps.

Zia, who arrived here early today, conveyed the four-day cease-fire offer by Iraqi President Saddam Hussein to a meeting of the Islamic foreign ministers tonight. It said, in effect, that Iraq will stop fighting from Sunday through Wednesday in the hope that negotiations on a permanent cease-fire can be started in that period.

Hussein qualified the proposal by saying Iraq would resume military operations if Iran continues to fight or attempts to reinforce its forces in the battle area.

The Iraqi president, in the message transmitted through Zia, also said his offer would be invalidated if Iran continues the "hurling of aggressive, rejectionist statements against a cease-fire" or fails to make "a clear public declaration" of its readiness to enter into negotiations immediately.

Because of these qualifications, there was widespread skepticism here that the move would alter Iran's adamant insistence that Iraqi forces give up captured Iranian territory.

That impression was reinforced by a letter sent earler today to U.N. Secretary General Kurt Waldheim by Iranian president Ablo Hassan Bani-Sadr. In it, Bani-Sadr reaffirmed the vow made Tuesday by Iran's leader Ayatollah Ruhollah Khomeini, to keep fighting until the Iraqis are expelled from Iran.

"So long as Iraq is in violation of our territorial sovereignty and Iraqi agents are involved in acts of aggression and sabotage within our boundaries, we see no use in any discussion," Bani-sadr told Waldheim.

His stance was reiterated here tonight by Jamal Shemirani, charge d'affaires of the Iranian U.N. mission. He said he had told the Islamic Conference meeting that the Iraqi offer was unacceptable and added: "While the aggression against us continues, there is no question of our accepting anything at all."

"u.S. officials here with Secretary of State Edmund S. Muskie refused any immediate public comment on the Iraqi plan. Privately, however, U.S. and other Western sources said the Iraqi moves seemed like a propaganda ploy or an attempt to buy time in which to consolidate the positions held by Iraqi forces inside Iran -- perhaps in preparation for a renewed military drive after the four-day pause.

Since the fighting began, Iraq has captured a sizable amount of territory within Iran. But stiff Iranian resistance has left pockets of Iranian forces still holding out. This is seen as slowing Iraq's timetable.

Iraq is demanding return of allegedly "unsurped" border territory and waters of the Persian Gulf, plus the return to "Arab sovereignty" of three small islands taken by Iran in 1971.

Earlier this week, Hussein wrote to Waldheim offering to accept a cease-fire if Iran agreed to those demands. He subsequently sent Waldheim another message proposing a cease-fire without mentioning any pre-conditions.

As a result, neutral observers here tonight tended to regard the latest Iraqi proposal as yet another attempt by Hussein to win a halt in the fighting while Iraq has control of at least part of the territory it wants.

The Islamic Conference's reaction to the proposal was seen by diplomats here as a reflection of Moslem countries' desire to stop the fighting before it spreads further in the strategic region. Diplomats also said the reaction reflects Iran's isolation within the Islamic bloc, whose membership is dominated by Arab countries siding with Iraq. Iran, while Islamic, has only a minority of Arabs.

In a reference to this isolation, Shemirani told reporters after tonight's meeting that he did not think Iran was being treated fairly by the other conference members. He refused to elaborate.

Earlier today, Zia, in a speech to the U.N. General Assembly, underscored the Islamic world's concern that continued fighting might spread and cause an intervention by outside countries such as the United States or the Soviet Union.

"An essential condition for the return of peace would be the observance of strict neutrality and noninterference in their internal affairs by the outside powers," he said.

Zia, who is to meet with President Carter in Washington Friday, also raised eyebrows among many Western diplomats here through elements in his speech that hinted at a possible "tilt" toward the Soviet Union.

In the prepared text of his speech, Zia blamed the conflict on "the unstable conditions created in a sensitive area by the pressures and counter pressures off superpower rivalry." But when he delivered the speech, Zia deleted the reference to the superpowers and spoke instead of the Persian Gulf region's "colonialist legacy" -- a remark that appeared to absolve the Soviet Union from blame and slap at the United States and such West European allies as Britian and France.