Allied warplanes Sunday kept up the round-the-clock bombardment of Iraqi positions, a U.S. B-52 crashed in the Indian Ocean after a bombing run and a U.S. military official said at least seven of the 11 Marines killed in fierce ground fighting last week were the victims of friendly fire.

A published report, meanwhile, said the Pentagon could begin the much anticipated allied ground offensive in as soon as 10 days, and Rep. Les Aspin, D-Wis., Chairman of the House Armed Services Committee, said it would be "dangerous" to make the ouster of Saddam Hussein an objective of the war.An Air Force B-52 bomber returning from a bombing mission with a crew of six crashed early Sunday en route to the Diego Garcia Air Base in the Indian Ocean, the Pentagon said. Three crew members had been rescued from the water but the remaining three were missing, the Pentagon said.

"There is no evidence that the aircraft went down as a result of hostile fire," the statement said. The bomber was returning to the air base on the Indian Ocean island 2,500 miles southeast of Saudi Arabia.

Marine Maj. Gen. Robert B. Johnston of the U.S. Central Command said at a briefing in Riyadh, the Saudi capital, that it was the U.S. military's "best estimate" that the huge bomber went down as a result of mechanical problems.

Johnston also said a Marine AH-1 Cobra helicopter crashed during a non-combat escort mission in Saudi Arabia, killing both crew members on board.

Discussing the deaths of 11 U.S. Marines late Tuesday in close fighting with Iraqi troops near the Saudi-Kuwaiti border, Johnston said investigators had "every reason to conclude" that an airborne missile had struck at least one light armored vehicle carrying seven of the slain soldiers.

Because the Iraqi forces had no warplanes in the area, Johnston said, it was likely that the seven Marines were killed by friendly fire.

"We have enough evidence right now, in the initial stages of the investigation, to say with some great certainty that (the Marines in) one of the light armored vehicles . . . (were) in fact killed by friendly fire," Johnston said.

At the time, a Marine officer at the scene noted that U.S. and Iraqi troops were fighting at distances of as little as 25 yards, making it difficult for allied air support units to distinguish between the two sides.

Iraq launched conventionally armed Scud missiles at Saudi Arabia and Israel early Sunday. The Scud fired at Saudi Arabia was intercepted by a U.S. Patriot air-defense missile, the U.S. Central Command in Riyadh said, but Saudi officials said debris injured 29 people in a residential area north of Riyadh.

A Scud also was fired at Israel late Saturday. No Patriots were fired at either Scud aimed at Israel. Neither caused any injuries, but Israel Defense Forces chief spokesman Brig. Gen. Nachman Shai said there was slight damage in the second attack. He would not say where the missiles hit.

Ironically, one of the Scuds fired at Israel "appears to have landed in Jordan," which lies between Israel and Iraq. Jordan officially has maintained neutrality in the war, but is closely aligned with Iraq.

In response to the Scud attacks, the Central Command issued a statement saying, "The counter-Scud patrols were on station throughout the night. Although these patrols did not preempt the three Scud attacks, they were still able to attack two of the three launch sites. Pilots reported seeing explosions at one of those sites."

On the ABC News program "This Week with David Brinkley," Defense Secretary Dick Cheney commented that Saddam "still has Scud capability, we assume he still has chemical capability tied to the Scuds, although we've never seen him use it."

Meanwhile, the Los Angeles Times quoted a high Pentagon official Sunday as saying an allied ground offensive could begin once military officials estimate about half of Iraq's combat vehicles and equipment are destroyed, and that this could be in as little as 10 days.

The newspaper quoted a highly placed Pentagon official who requested anonymity as saying the U.S.-led air campaign has had a "dramatic effect" on Iraq's 545,000 troops and their ground weapons.

Unless weather or some other factor disrupts the U.S. air war schedule, the Iraqi forces would be softened up enough for an allied ground assault in 10 to 20 days, the official told the Times.

The comments reveal the most precise assessment so far of the how much damage U.S. military planners want to infict on Iraq forces.

The Pentagon official quoted by the Times cautioned that war planners will not be able to determine exactly when the 50 percent target of Iraqi damage is reached, and emphasized any ground battle would be a "slugging match" with substantial U.S. casualties.

Aspin, appearing on the NBC News program "Meet the Press," expressed concern that "we're about to do something dangerous here" by broadening allied aims to ensure Saddam Hussein is no longer in power after the war.

"Getting rid of Saddam Hussein might come as a byproduct of getting him out of Kuwait," said Aspin, who has been one of the more outspoken congressional Democrats supporting President Bush's gulf policy.

"If it doesn't, making it one of the aims is going to mean that somebody's got to then go on to Baghdad," Aspin said. "It means that this war is going to take a lot longer, and it's going to be a lot more casualties.

"The cost - in terms of time and casualties, of expanding the war aims to include getting Saddam Hussein - is going to be very, very large," Aspin said. "And I think we ought to give that a lot of consideration before we just automatically expand those aims."

A senior Bush administration official said last week that Saddam's remaining in power "would be conceivable, however undesirable."

Cheney, on ABC, tried to discount any political aims by the United States and its allies: "If we achieve our objective of getting Saddam Hussein out of Kuwait, if we're able to destroy his offensive military capability, which we're well on our way to doing now, then I think we will have achieved our objectives."

He said if Saddam remained in power after the war, the international community could "maintain some sanctions" against Iraq "to deny him the ability to rebuild that military force that he's used against his neighbors."

In Saudi Arabia, the U.S. military, responding to reports that some soldiers fear their chemical suits have lost their effectiveness, said replacements would be delivered to troops in time.

A news media pool report said some Army divisions were awaiting replacements for suits first used Jan. 18 when Iraq began firing Scud missiles at Saudi Arabia.

Soldiers in the Army's 1st Armored Division said they were told before the war that their suits would begin to lose their effectiveness within two weeks of being removed from their packages.

But the soldiers, stationed in the front lines near the border with Kuwait, said that with replacement chemical suits yet to be delivered, they were being told the suits remain effective for 30 days.

Air Force Capt. Ray Martell, a spokesman for the U.S. Central Command in Riyadh, said he could not confirm whether all U.S. troops had received replacement suits. But he said the suits are effective for at least 22 days and "we're prepared to replace them after that 22-day period."

In other developments:

-Johnston told the Riyadh briefing that allied planes had conducted 2,500 sorties Sunday, bringing the total to more than 41,000 since the war began on Jan. 17. Iraqi radio, however, claimed a sharply lower number of allied raids over Iraqi territory - only 17 overnight. Saturday, Iraqi radio reported only 18 allied raids. Before Saturday, Iraq was claiming more than 100 allied raids over Iraqi territory every 24 hours.

-It was "significantly quiet" on the ground Sunday, Johnston said, but he noted that Iraqi land forces could be expected to conduct some intermittent "probing action" because they have no air reconnaisance capability along the Saudi-Kuwaiti border. He also said the Iraqi naval forces had been reduced to the point where there was "absolutely no activity on the water" Sunday.

-A senior Sri Lankan Cabinet minister said U.S. military planes and ships en route to the Persian Gulf likely will be permitted to refuel at the Indian Ocean island nation. The minister, who requested anonymity, said approval was expected at a Cabinet meeting at an unspecified time later this week.

-Nine German peace activists, returning to Bonn after living in Baghdad since the outbreak of the war, confirmed reports that continuous allied bombings have almost destroyed Iraq's infrastructure. "There is hardly any water during the day, almost no electricity, and food is rare," said Alexander Kriegsheim, a member of the group, describing conditions in Baghdad.

-Pope John Paul II reiterated his appeal for an end to the gulf war and reminded the world of the Christian commandment that forbids killing. He urged the crowd gathered in front of St. Peter's basilica to proclaim the right to life "against this war that continues to be fought in the Persian Gulf region and constitutes a growing threat to all humanity."

-Members of the Kuwaiti resistance told a Kuwait support group in Cairo, Egypt, that Iraq's defeat at Khafji by allied forces last week has caused morale to deteriorate among Iraqi troops stationed in Kuwait.

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(Additional information)

Brits take aim (at us)

While the Union Jack and Stars and Stripes are on the same side in the gulf war, the British are fighting against a country that sounds like "Eer-awk" while Americans are bombing "I-rackies."

"This war, run by the Americans and (more to the point) largely broadcast by them, is blowing breaches in the redoubt of our language and our pronunciation of it," writer Simon Heffer harrumphed.

Heffer beefed about television reporters talking of "lootenants" instead of properly British "leftenants," of "missels" instead of "miss-aisles," of Patriot missiles beginning "pate" instead of "pat."

"Perhaps the most boggling usage encountered so far," Heffer added, "was uttered by an American military technical expert who, when the missile attacks began on Tel Aviv and Riyadh, was discussing `an-tie missel missels' with an American interviewer.

"Neither batted any eyelid when, in mentioning the `I-racky' capability of dealing with `Paytriot missels,' the expert ruled out the possibility of any `I-racky an-tie an-tie missel missel missels."'