DUBAI, UNITED ARAB EMIRATES, AUG. 30 -- Iraqi jets struck a major Iranian offshore oil facility and apparently a tanker for the second straight day today, as U.S. Navy warships escorted two more reflagged Kuwaiti tankers into the Persian Gulf. Iran threatened to retaliate against any ships allied with Baghdad "regardless of the flag they have hoisted."

By carrying out the air strikes today, Iraq pursued a promise made yesterday by President Saddam Hussein to cut Iran's seaborne economic lifelines. An Iraqi military communique reported that a wave of warplanes launched strikes in the northern gulf on the main Iranian oil terminal at Kharg Island and on a "very large naval target," standard Iraqi military terminology for a tanker or large merchant ship.

{In Washington, Undersecretary of State Michael H. Armacost, interviewed on NBC's "Meet the Press," called the timing of the Iraqi attacks "deplorable" since they came at a time when Iran was under pressure to accept a U.N. Security Council resolution demanding a cease-fire in the nearly seven-year-old gulf war. Story on Page A22.}

{But Armacost also called Iraq's decision to renew the attacks "not entirely unexpected" and "understandable" given Iran's refusal to accept the resolution. Iraq wants a comprehensive cease-fire on "land, sea and air," Armacost explained.}

Iran continued the ground war with Iraq during a tacit 45-day cease-fire in the tanker war, shattered yesterday by the renewed Iraqi air strikes. The attacks seemed to indicate that Iraq is unwilling to accept a cease-fire in the sea war without a cessation to fighting on the ground, gulf observers noted.

Near Kharg Island, supply vessels reported seeing thick clouds of smoke rising from its jetties, Reuter news agency quoted shipping sources as saying. Kharg Island, although damaged in previous Iraqi attacks, has been channeling about 2 million barrels of Iranian crude a day to loading points to the south. The shipping sources could not confirm the Iraqi claim that a tanker had been hit.

Iran warned that in retaliation for the renewed attacks against its oil and shipping facilities in the gulf, "any vessel belonging to participants alongside Baghdad in the imposed war, regardless of the flag they have hoisted, will be attacked," Tehran radio said.

Iranian Foreign Minister Ali Akbar Velayati sent a letter to U.N. Secretary General Javier Perez de Cuellar, vowing that "Iran will not leave these attacks unanswered, and Iran's retaliation . . . may also include facilities which equip Iraq and beef up its war machine." Iran has regularly accused Kuwait of directly aiding Iraq in the war. Tehran charged that the United States had "collaborated" in yesterday's Iraqi raids.

Shipping sources here and western journalists flying off the coast reported that six U.S. Navy vessels sailed through the Strait of Hormuz, the mouth of the gulf, early this morning, leading the two reflagged tankers northward to Kuwait. A photographer who observed the vessels from a helicopter said the convoy was preceded by mine-sweeping Sea Stallion helicopters from the amphibious assault ship USS Guadalcanal.

The convoy entered the gulf less than 24 hours after Iraq broke a six-week lull in the tanker war with Iran by launching air strikes against a number of its offshore oil installations and possibly two tankers. Shipping sources said a 236,807-ton Iranian supertanker was set ablaze yesterday in the southern gulf, and Iraq claimed to have hit a "large maritime target" in the northern gulf.

{The master of the supertanker reported hit yesterday, the Iranian-owned Alvand, telephoned the British Broadcasting Corp. in London to report that his ship was undamaged, the Los Angeles Times reported. No other details were available.}

A number of shipping sources anticipated Iranian retaliatory attacks against Kuwaiti or U.S. vessels -- or perhaps targets belonging to Saudi Arabia, with whom Iran's relations have suddenly become strained. But a nonwestern diplomat suggested that Iran may yet prefer to avoid a direct confrontation with the United States.

"One has to remember to separate Iranian rhetoric from Iranian actions. Iran may threaten the United States, but it has many alternatives to attacking them," he said. "It could strike the Iraqis on the land front or could attack some Kuwaiti target that the United States is not defending."

"If the Iranians were actually seeking confrontation with America, they could have had it dozens of times already," the diplomat said.

A U.S. Navy spokesman aboard the La Salle, the flagship of the Middle East Force conducting the escort operation, would not say whether the group had altered its operating procedures in the face of heightened tensions.

The convoy that entered the gulf this morning sailed through a dusty haze that limited visibility, according to journalists who flew to observe ships. Behind the mine-hunting helicopters and two warships, the reflagged tankers Surf City and Chesapeake City sailed in single file. Between them was the USS Raleigh. Two other warships followed, while a frigate sailed alongside, several miles toward the Iranian coastline.

The arrival in the gulf of the USS Raleigh reinforced the Navy's ability to deal with its most difficult threat so far: mines. The Raleigh, an amphibious transport dock ship, is carrying four small mine-sweepers of a type used in the Vietnam War to clear rivers.

The craft will supplement the Sea Stallion helicopters, whose ability to sweep for mines has been hampered by difficult weather. Reporters said they did not see the newly arrived mine-sweeping boats in use today, but spotted several small craft mounted on the Raleigh's deck.

The Navy spokesman, Lt. Cmdr. Steve Honda, said in a telephone interview that the force, comprising 11 ships, places about 4,500 U.S. personnel on the waters between Kuwait and the Gulf of Oman, just below the Persian Gulf.

Although the Navy declines to comment on the placement of its vessels, ship sightings make clear that most of the force is currently within the Persian Gulf, the area of greatest risk.

Iraq also carried out attacks inside Iranian territory today, flying a total of 178 combat missions in strikes against oil pumping stations in western Iran and Iranian troop positions at the war fronts, the Iraqi military communique said.