Federal prosecutors have asked a judge to drop charges against the Afghan-born brother-in-law of Osama bin Laden's bodyguard, saying a key overseas witness was unavailable to testify.

The decision was a striking reversal in the case against Ahmadullah Sais Niazi, who had been accused by prosecutors of lying about his ties to terrorist groups on his citizenship application.

The government alleged in court papers that Niazi was a dangerous threat who had spoken of jihad, traveled to Pakistan to meet with a high-ranking al-Qaida leader, and associated with the Taliban and a terrorist organization called Hezb-e-Islami, which fights international and U.S. troops in Afghanistan.

Niazi had been scheduled for a November trial on charges of perjury, procurement of naturalization unlawfully, passport fraud and making a false statement. He could have faced up to 35 years in prison if convicted of all the charges.

His attorney, Chase Scolnick, declined to comment because a judge has not yet signed off on the dismissal motion. Niazi was not immediately available for comment, Scolnick said.

The government made its motion Wednesday, requesting dismissal without prejudice, which means charges could later be refiled.

"After considering all aspects of the case, including the unavailability of an overseas witness, the government decided that it could not move forward with the prosecution," Thom Mrozek, a spokesman for the U.S. attorney's office, said in a prepared statement.

The statement said no further comment would be provided.

The FBI, which built the case against Niazi, referred calls to the U.S. attorney's office.

Niazi's case grabbed national attention when he was arrested in February 2009, and a former FBI informant named Craig Monteilh soon went public with his involvement in building the case.

Monteilh, 48, said he infiltrated Niazi's Southern California mosque for the FBI by pretending to be a half-French, half-Syrian Muslim convert.

Once there, he secretly filmed and recorded dozens of worshippers at mosques, including the Islamic Center of Irvine, where Niazi worshipped, according to court papers.

The AP has independently confirmed that Monteilh worked for the FBI as a mosque informant from 2006 to 2007.

Monteilh later sued the FBI for $10 million, alleging he was mistreated by the agency. That lawsuit was thrown out, but the fitness trainer filed an amended complaint last month.

He has also cooperated with Niazi's defense attorney and joined forces with the American Civil Liberties Union to help them build a civil case against the FBI over its spying techniques, according to legal documents obtained by the AP.

Muslims who followed the case said they were pleased with the government's move to dismiss the case and believed Niazi had been charged because he declined to become an informant for the FBI.

They noted Niazi had spent more than 18 months in home detention that was downgraded earlier this year to a curfew lasting from 7 p.m. to 7 a.m. He also wore a tracking device on his ankle.

"We welcome this corrective action by the government and the FBI," said Hussam Ayloush, executive director of the Council on American-Islamic Relations in greater Los Angeles.

"At this point the government — and specifically the FBI — owes Mr. Niazi, his family and the Muslim community at large a major apology for ruining his reputation and parading him as some sort of vicious terrorist," Ayloush said.

Experts familiar with the prosecution of terrorism-related cases said it was unusual to request a dismissal of such a high-profile case, particularly after the passage of so much time. The trial has been postponed several times.

Patrick Rowan, former assistant attorney general for national security, said Monteilh's behavior following Niazi's arrest could have played a role in the decision to request a dismissal.

"Ordinarily, you would have plenty of corroboration for what an informant was saying," said Rowan, now a partner at a private law firm.

"But if the informant is 60 percent of the case, you can imagine that if the 60 percent goes away, then you're looking at a case that may not be worth pursuing," he said.

(This version CORRECTS Corrects location of court to Santa Ana instead of Los Angeles. Adds quote, details.)