Six Iraqi helicopters crossed the border from Kuwait into Saudi Arabia yesterday in the first major defections from President Saddam Hussein's air force, U.S. military officials said yesterday.

Two of the helicopters, bearing an unknown number of defectors, ran out of fuel and made forced landings in the Saudi desert just south of the border with Kuwait, Associated Press quoted Lt. Col. Mike Gallagher, chief of media at the Riyadh Joint Information Bureau, as saying. The other four were escorted by F-15 fighters to the Ra's al Khafji air base about 11 miles south of the border. All of the Iraqi airmen were in Saudi custody last night.

The Iraqi government denied the Pentagon report, calling it "wishful thinking" and part of a U.S. effort to foster confusion. "This is a baseless and unfounded report," Information Minister Latif Nassif Jassim told the official Iraqi News Agency. "What assures us that this is untrue is that there were no Iraqi {air} exercises at all today."

Few details were immediately available about the episode, including the number of Iraqi airmen, their aircraft or their reasons for defecting. It could not be learned last night whether U.S. or Saudi warplanes escorted the helicopters to the al Khafji base.

There are no attack helicopters in the Iraqi air force, according to the Annapolis-based U.S. Naval Institute. Iraq flies Soviet-made Mi-10 Harke heavy lift helicopters, Mi-4 Hound, Mi-6 Hook and Mi-8 Hip transport craft, German-made BK-117 search and rescue helicopters and Wessex 52 maritime patrol craft.

Iraq has only 162 transport helicopters in its air force, the Naval Institute said. Iraq, considered at a disadvantage in the mobility of its forces, will be further constrained by the loss of six helicopters.

Saudi and Kuwaiti sources say more than 300 Iraqi troops have defected since the start of the confrontation over Baghdad's invasion of Kuwait.