WASHINGTON (AP) _ Iraq is using decoys to thwart allied efforts to wipe out Scud missile launchers, Pentagon officials said Monday, while congressional sources said the campaign was being hampered by persistent hostile fire as well.

''They do use decoys and they use them well,'' Lt. Gen. Thomas Kelly told reporters at a Pentagon briefing. He said allied warplanes are working ''big time'' to take out the remaining launch sites, which Iraq has used to fire rockets into Israel and Saudi Arabia.

He cited bad weather as hampering the operation, and said the Iraqis' use of decoys was ''somewhat of a problem. I can't quantify it.''

Navy Rear Adm. John McConnell said that despite the massive air operation - 8,100 sorties in the five-day war - Saddam Hussein and the military command are ''still in control of military activity in the country.''

Even so, Pentagon spokesman Pete Williams said Operation Desert Storm is ''going more or less according to plan,'' and Kelly said he believed that a protracted ground war could still be avoided as the allies press their campaign to evict Iraqi forces from Kuwait.

Kelly disclosed that Iraq had fired one additional Scud missile toward Saudi Arabia a short while earlier, but said it landed harmlessly in the Persian Gulf near Jubail.

Later, witnesses in Riyadh, the Saudi capital, reported seeing what appeared to be another Scud interception by a Patriot missile high over the city. Diplomatic sources reported that two more Scuds fell harmlessly in the desert and still later military authorities reported yet another Scud destroyed by a Patriot

The military has said earlier that nine out of 10 previous Scud missiles firings into Saudi Arabia before Monday were shot down by American-made Patriot missiles. The other one also landed in the water.

In other news from Saudi Arabia, pilots of A-10 ''Warthog'' Air Force ground attack planes reported escorting a helicopter in an eight-hour operation that ended with the successful rescue of the pilot of a Navy A-6 bomber after an A-10 destroyed a truck headed for the downed pilot's location.

Kelly continued to provide an upbeat assessments of the war, but he repeatedly refused to give specific damage estimates or provide answers to other types of questions. Sometimes he cited weather constraints on intelligence gathering, and sometimes he didn't. At one point, he said: ''You've got to remember that we're in a war. You've got to remember there is another side in this war.''

Kelly said that once pilots get close to Scud targets, they generally can tell which ones are decoys. A knowledgeable Pentagon officer said Saddam has been known to use wooden decoys that mock the silhouette of the mobile and fixed Scud missile launchers.

In London, British Armed Forces Minister Archie Hamilton said allied pilots may have destroyed some of these decoys.

Kelly disclosed that the number of American forces in Operation Desert Storm had swelled to 472,000, an increase of 7,000 over the weekend. He said nine American warplanes had been lost, and 14 American troops were listed as missing in action.

Williams said that 17 Iraqi planes have been destroyed.

In Saudi Arabia, U.S. military sources said a crater in a Riyadh residential neighborhood may have been made by falling debris from the collision of an Iraqi missile and an American missile that intercepted it.

They said investigators found pieces of metal tentatively identified as coming from an Iraqi Scud and a Patriot anti-missile missile after the blast, which damaged a building and dug a hole five feet deep in a vacant lot.

Two Patriot missiles in Riyadh were fired by accident over the weekend when their automatic fire control systems mistook an unusual radar reflection from the atmosphere for an incoming missile, according to a statement from Fort Bliss, Texas, quoted in Tuesday editions of the El Paso Times. Batteries from Fort Bliss are assigned to Riyadh.

On Capitol Hill, congressional sources said the search for Scud launchers was being hampered by the sporadic nature of the Iraqi attacks, cloud cover and the need for search planes to fly at high altitudes to avoid rockets and antiaircraft fire. Administration officials briefed members of Congress on Monday.

''We'd be a lot better off if we could fly lower,'' said a source who said the military does not want to risk pilots and planes unnecessarily. The source insisted upon anonymity.

Lawmakers said the military appears content for now to stick with its air war, where the allies hold an advantage.

''There's a sense he's hunkering down and waiting us out,'' Rep. Tim Penny, D-Minn, said of Iraq's Saddam Hussein. ''But I don't think there's any sense that his approach is going to wear us down....I don't think he's in a position where he can mass a major offensive. He really doesn't have much choice except to take a licking and see if he can keep on ticking.''

''My sense is there's no hurry to start the ground war, and there shouldn't be,'' added Rep. Thomas Downey, D-N.Y.

Generally, lawmakers urged Americans to resist the temptation to think the war will be brief or painless.

''The battle's going according to plan, but we're not going to have a victory toast next week or the week after,'' said Sen. Christopher Bond, R-Mo.

''You can't plan for an easy war,'' added Sen. John Glenn, D-Ohio. He said Saddam Hussein's forces are proving to be tough targets. ''Who could take all this (bombing) and still sit there? That's a resilience I don't know we quite expected,'' he said.

Williams, echoing President Bush and other officials, demanded that Iraq comply fully with international accords dealing with prisoners of war. He said it was impossible to determine whether any captured Americans ''Have been subject to any mistreatment,'' either physically or mentally.

Williams also said Bush had signed an executive order giving preferential tax treatment to the men and women of Operation Desert Storm. Enlisted troops in the region don't have to pay federal income tax on their military pay. Officers get a $500 a month tax-free, he said.

Kelly said the allied pilots continued to work hard to eliminate the Scud missile launchers that Saddam has used to fire on Israel and Saudi Arabia.

It's ''one that we're on big time and one that we will stay on big time,'' he said. ''The minute the missile is off the launcher'' pilots begin pursuit, he said. But Iraqis are working just as hard to move the launcher before allied planes can get overhead, he said.

Monday's shot raised to 18 the number of Scuds known to have been fired by Iraq since the war began Jan. 17. Confirmation of Monday night's shot would make it 19. American commanders are buoyed by the announced 11-for-11 success of the Patriots, which cost $1 million each and are undergoing their first combat test in the 11th year of production following 15 years of development marked by controversy over technical problems.

The Patriot uses advanced phased-array radar to spot, identify and track an incoming missile, then attacks it with a 200-pound explosive warhead.

''Every Scud missile that has been launched at Riyadh or Dhahran has been successfully engaged by a Patriot missile,'' Maj. Gen. Burton R. Moore, chief of plans for U.S. Central Command, told the daily news briefing.

''We have taken some of them out, but we are nowhere near our objective,'' he said. ''We have not achieved 100 percent of our objective in taking out fixed and mobile launchers.''