A suspected Al Qaeda cell leader in the custody of a foreign government has acknowledged firing a missile at a U.S. military plane in Saudi Arabia in recent months, a U.S. official said on Wednesday.

The man, who is Sudanese, acknowledged shooting a shoulder-fired SA-7 surface-to-air missile at an American plane taking off from Prince Sultan Air Base, south of the Saudi capital of Riyadh, the official said, speaking on the condition of anonymity.

The man was believed to have been captured in Sudan, but isn't in Sudanese custody.

In May, Saudi security guards found the missile launch tube about two miles from the nearest runway, inside the base's outer perimeter fence and near an inner fence.

No aircraft had reported detecting an incoming missile, however, and it was unclear when the Soviet-made missile had been fired.

The discovery promoted the FBI to issue warnings to U.S. police departments in late May.

The FBI sent the message May 22 urging state and local police departments to remain vigilant, but cautioned there was no indication of any attack plot.

"We have no information to indicate Al Qaeda is planning to use any type of missile or weapons systems against commercial aircraft in the U.S.," the bulletin said.

Instead, the FBI indicated it believes Al Qaeda may try to use such weapons against U.S.-led military forces in the region.

The missile firing was first reported by ABC News.

About 4,500 U.S. troops and an unspecified number of American warplanes use the desert base.

The presence of U.S. troops in Saudi Arabia, home to Islam's holiest sites, since the Gulf War is one of Usama bin Laden chief stated reasons for attacks on Americans.