KUWAIT, JULY 19 -- As the U.S. military presence and threats from Iran have escalated prior to this week's inaugural voyage of a Kuwaiti supertanker flying the American flag, western diplomats here are hoping that a United Nations vote Monday for a cease-fire in the Persian Gulf war will forestall any direct confrontation involving the United States.

Amid preparations for the U.S. "reflagging" of 11 Kuwaiti tankers, a U.S. Navy mine-sweeping team today cleared or detonated eight mines at the channel entrance to Kuwait's oil loading port. A Kuwaiti Defense Ministry spokesman said tonight that the team worked with Kuwaiti helicopters and Saudi Arabian naval vessels in the mine-clearing operation.

Saudi Arabia has agreed to continue helping mine-clearing efforts once the U.S.-flagged ships begin moving Kuwait's petroleum products through the gulf, a western diplomat said.

Diplomats here said recent public statements by Iran -- that it will attack gulf shipping only in retaliation for Iraqi strikes on its oil facilities and tankers -- have created an opportunity to defuse the rapidly mounting tensions along this strategic waterway.

"When it comes to the reflagging operation this week," one western diplomat said, "there is a good chance, if everyone behaves according to his public statements, that the tanker war will cease and the first reflagged ships will pass unmolested through the gulf."

Although Iran has declared that it will not abide by any U.N.-voted cease-fire, it has also said its shipping attacks are strictly retaliatory.

"If Iraq stops its mischief and does not attack our ships, there would be no aggression against any ship on our side, whether that ship carried U.S. or any other flag," Iran's parliament speaker Hojatoleslam Ali Akbar Hashemi Rafsanjani said after a July 9 meeting of Iran's Supreme Defense Council.

Iran gave evidence of its intentions, the diplomats said, following the May 17 attack by an Iraqi warplane on the USS Stark, a U.S. Navy vessel. For several weeks afterward, Iraq froze its attacks against Iranian naval targets. And, during the same period, Iran halted its raids against Kuwaiti shipping.

When Iraq resumed its attacks in late June, Iran also loosed seaborne Revolutionary Guards against ships going to or leaving Kuwait.

Rafsanjani's statement and similar ones from leaders in Tehran have convinced some western diplomats that the key to success or failure of U.S. intervention in the "tanker war" will be whether Iraq will extend any truce to the gulf.

"Iraq is under considerable pressure not to take up attacks on shipping" if the U.N. resolution passes Monday afternoon, one western diplomat said. "This is a very important key to what is happening: How will the Iraqis behave?"

This diplomat suggested that Iraqi President Saddam Hussein, who launched the war in 1980 and now is seeking to end it, may become "caught by his own rhetoric" since a cease-fire in the tanker war will also allow Iran's oil exports to pass unmolested through the gulf.

This western official said he believed that if Iran continued to pursue the land war against Iraq after a U.N.-declared cease-fire, Iraq's president would be forced to resume attacks on Iran's vital oil supply lines in the gulf.

If that happened as the American Navy takes up its policing role in the waterway, "the risk of something going wrong will increase tremendously," the official said.

The U.N. Security Council vote on a cease-fire resolution, drafted after months of negotiation, was scheduled for Monday after strong urging from Reagan administration officials who hope that it can be passed before the U.S.-protected ships begin sailing in the gulf. Vernon A. Walters, U.S. ambassador to the United Nations, predicted during the weekend that "we are going to get a resolution."

In a related diplomatic campaign, Kuwait has sent its envoys to 55 Arab and Islamic capitals in the past month seeking international attention to the threat posed by escalation of the conflict. And, in an unusual public appearance, Kuwait's crown prince, Sheik Saad Sabah, has invited more than 150 international journalists to a news conference Monday on the gulf situation.

The moves by Kuwait's leadership to further internationalize the threat to Kuwait and to gulf shipping were seen by western diplomats as a reaction to escalating Iranian threats against Kuwait's shipping as well as its territory.

The magnitude of the diplomatic campaign has prompted some western diplomats to speculate that there may be new intelligence information indicating Iran is developing contingency plans to "open a second front," as one put it, on Kuwaiti territory.

One senior western diplomat said there have been recent "indications" that Kuwait has been strengthening its defenses on Bubiyan Island, a marshy frontier that western analysts have long feared might be used by Iran to outflank Iraq's heavily fortified southern defenses between the port of Faw and Basra. Such a move might also cut the highway in Kuwait over which war materiel is transported to Iraq.

"Kuwait's strategy clearly would be to make some defense to delay Iranians, but it's quite clear that Iran would be able to march right through them," one diplomat said.

The diplomat said he was concerned that none of Kuwait's neighbors, including Saudi Arabia, has the military strength to meet such a threat, and, in the "internationalized" environment of the gulf war zone, it would fall to the United States, to commit its forces to Kuwait's defense.

Some western officials in recent weeks also have expressed concern that Iran's hit-and-run naval attacks may be shifting into even shallower waters near the Saudi Arabian coastline where U.S. warships would be unable to operate. And, the waterborne Iranian commandos have begun using incendiary grenades, whose white phosphorus explosive is considered a greater threat, to ignite heavy crude oil cargoes that have proved resistant to ignition by ordinary grenades.

One such attack occurred on June 27 against a Norwegian registered supertanker, Mia Magrethe.

The ship had just left Kuwait's Ahmadi oil port for Saudi Arabia's Ras Tanura terminal when three Iranian speedboats came alongside just after midnight and fired 40 rocket-propelled grenades against the ship and raked its crew quarters with automatic weapons.

The attackers missed with half of their rounds, and scored three direct hits on the only empty tank compartment. The 14-minute attack left the supertanker without power and in waters so shallow it nearly went aground before salvage tugs pulled it into deeper waters.

A western diplomat said the attack demonstrated that the unconventional Iranian speedboats, capable of running at 60 miles per hour in very shallow waters, would be elusive targets for American naval escorts.