DUBAI, UNITED ARAB EMIRATES, SEPT. 11 -- U.N. Secretary General Javier Perez de Cuellar arrived in Tehran today against a backdrop of cautious Iranian comments about the prospects of his mission to seek a way to implement a Security Council-mandated cease-fire in the war between Iran and Iraq.

As he flew into the Iranian capital, the war front between the fiercely antagonistic neighbors fell silent and shipping sailed calmly in Persian Gulf waters. It was a sharp contrast to fierce land and sea attacks over the past two weeks.

Perez de Cuellar was met by Foreign Minister Ali Akbar Velayati and held initial talks with him this evening, United Press International reported. He is expected to meet with top Iranian officials Saturday and Sunday and then move on to Baghdad for two days of talks with officials in the Iraqi capital.

The internationalization of the gulf conflict continued today, as French ships began sweeping for mines in waters of the Gulf of Oman off the United Arab Emirates' port of Fujayrah, according to witnesses and shipping sources.

It was the discovery of mines in the Gulf of Oman in early August that signaled a spread of the conflict out of the Persian Gulf and put new pressure on European nations to increase their military presence in the region. The French mine sweepers, which just arrived in the area, are part of that buildup.

In London, the Defense Ministry said Britain had agreed to protect two Dutch mine sweepers being sent to the gulf by the Netherlands. "The Dutch will benefit from the level of protection available to our own mine sweepers," a ministry spokesman told Reuter.

In a measure of further cooperation, the spokesman also said that Dutch and Belgian naval teams had met with British counterparts to develop a coordinated approach to sweeping gulf waters for mines.

It is this increased international concern that contributed to the July 20 Security Council resolution that called on Iran and Iraq to declare a cease-fire in their conflict, withdraw to recognized international borders and exchange prisoners. The resolution was adopted under a section of the U.N. charter that provides for sanctions if there is no compliance.

Perez de Cuellar, according to sources, will be trying to find some bridge between Iran's limited expressions of willingness to cooperate with the U.N. process and Iraq's hard-line position that its cooperation depends on Iranian compliance with the total measure.

Iranian President Ali Khamenei and Ali Akbar Hashemi Rafsanjani, the influential speaker of parliament, made it clear today that Iran welcomes the U.N. official's mission. It was equally clear, however, that Perez de Cuellar should not expect Tehran suddenly to abandon political positions it has held through almost seven years of war.

Khamenei told thousands of Iranians gathered for Friday prayers that "we gladly receive the secretary general and are ready to listen to just words. We will listen to words of truth from anyone and then accept it. But we will not accept the unjust word."

This attitude contrasted sharply to the one that met Perez de Cuellar's predecessor, Kurt Waldheim, who was manhandled by angry crowds when he arrived in Tehran in January 1980 on a mission to try to gain the release of Americans being held hostage.

Rafsanjani also spoke of a willingness to discuss a cease-fire, but only after Iraq is named as the aggressor in the conflict. The official Iranian news agency IRNA quoted Rafsanjani as telling the British Broadcasting Corp. in an interview that this is "the only key to solve the issue. . . . It is a positive point which must take place before a cease-fire is announced."

Iran has rejected previous U.N. resolutions on the gulf war as unfair or one-sided but has neither accepted nor rejected the latest. "We saw some positive points . . . and announced our readiness to hold negotiations," Rafsanjani was quoted as saying.

Despite his insistence on labeling Iraq the aggressor, commentators have noted that Iranian statements on the latest effort to end the conflict have dropped earlier strident demands for the removal of Iraqi President Saddam Hussein and the payment of massive reparations. Although one or both of these issues could reemerge, it is being taken as a positive sign that the atmosphere in Tehran permits a lowering of the threshold of public rhetoric.

In what could be interpreted as a U.S. gesture toward preparing the way for Perez de Cuellar's mission, a top State Department official was quoted as telling reporters in Washington yesterday that Baghdad's recent resumption of large-scale attacks in the gulf was "short-sighted from the Iraqi standpoint, but they don't listen to us."

The U.S. official placed his criticism of Iraq in the context of jeopardizing chances for a U.N.-mandated arms embargo if Iran refuses to accede to the cease-fire. Nevertheless, it also could be taken as an effort to convince Iran that Washington's position is not one-sided.

Iraq has said it would accept the cease-fire call, but only if Iran accepts all its provisions.

Other commentators from Washington also have spoken less stridently about Iran recently. Joseph Sisco, a former senior State Department official who has frequently been used as a special U.S. envoy, told a BBC interviewer yesterday, for example, that U.S. officials had noted that Iran had avoided attacks near U.S. Navy ships escorting reflagged Kuwaiti tankers in the gulf.

"Western military pressure in the gulf bulwarks the secretary general's mission," Sisco said. "We have created a very significant bargaining chip. The Iranians will not accept or reject the secretary general but will give him enough to go back home and report that there is room for maneuver, a basis for further intensive consultations. The U.S. is ready to give Iran more time."