U.S. and Saudi forces began a six-day amphibious exercise in the Persian Gulf Thursday. The exercise, code named "Imminent Thunder," involves 1,000 U.S. Marines, 1,100 aircraft and 16 ships.

Iraq has termed the exercise a "provocative act" because it is being held close to occupied Kuwait.The exact location of "Imminent Thunder" was not revealed because of military policy, and a news blackout was imposed for the initial phases of the operation.

No live ammuniton will be fired in the operation. But it will involve the largest use of aircraft in a single training exercise since U.S. forces were deployed in the region in August.

There have been three previous amphibious exercises in the Persian Gulf, but they were believed to have been held further south.

Also Thursday, Syria and Egypt rejected a proposed Arab summit on the Persian Gulf crisis, effectively killing chances for the gathering that Morocco's king said was possibly the last chance for peace.

Presidents Hafez Assad of Syria and Hosni Mubarak of Egypt became the latest Arab leaders to join Saudi Arabia in rejecting the summit. They said they were doing so because Baghdad insisted upon keeping Kuwait.

Saudi Arabia said Wednesday it would not participate in the summit unless Baghdad promised beforehand to leave Kuwait, which it invaded Aug. 2.

In other developments:

-Two American diplomats arrived in Amman, Jordan, on Thursday's regularly scheduled flight from Baghdad. The State Department said two Americans were to leave Iraq, but did not release their identities. "I'm not a hostage," said one, who was carrying an orange bag that looked like a diplomatic pouch.

-A poll sponsored by an arms-control group found that most Americans oppose going to war without a congressional declaration and nearly half prefer to give a U.N.-ordered embargo on trade with Iraq more time.

-The state Iraqi News Agency announced that President Bush will go "on trial" in absentia next month in Algeria for "inhuman policies and planning aggression against the people of Iraq."

The trial will begin Dec. 10 in Algiers in an international court of justice, INA said. It quoted the secretary-general of the Arab Jurists Federation, Shibeeb al-Maliky, as saying the trial would be held in accordance with rules used by the Nuremberg courts that tried Nazi war criminals.

-The first of several hundred khaki-colored M1A1 Abrams tanks, to be repainted in desert camouflage, rolled off a ship in Saudi Arabia Wednesday night. The tanks will replace M1 tanks in all front-line Army units in the country, with better protection from chemical and biological warfare, a larger gun and thicker armor. They will face Iraq's Soviet-made tanks.

"The M1 is better than anything the Iraqis have," said Army spokesman Maj. Douglas Bidle, 38, of Arlington Heights, Ill. "The M1 gave us an edge. This is a better tank, so obviously this is an even better edge."

Jane's Defense Weekly reported last month that 350 M1s would be swapped for M1A1s. The Pentagon has said all tanks will be switched by the end of the year.