He's dedicated his whole life on that cause.

Though the charges are not related to espionage, the arrest adds another strain to the already difficult relationship between the U.S. and Pakistan, which suffered after the U.S. found Osama bin Laden hiding inside Pakistan and killed him without telling the government there.

ISI has a complicated relationship with U.S. intelligence. The agency is a crucial ally in the war on terrorism but also works against the U.S. at times, including running double agents against the CIA.

"Dr. Fai and the Kashmiri freedom movement have nothing to do with the ISI," said Nadim Malik, a close associate of Fai and the executive director of the advocacy group Kashmir Mission USA.

Fai has donated to congressional campaigns of both parties for years. His donations include $250 to President Barack Obama in 2008; a total of $4,500 to the National Republican Senatorial Committee in 2004 and 2008; and $250 to the Democratic Senatorial Campaign Committee in 2009. Prosecutors said none of the recipients knew the organization was a front for money from Pakistan.

Zahid Bukhari, the president of the Islamic Circle of North America who says he's known Fai for years and used to teach at Georgetown University, said he found the accusations stunning.

"It doesn't make any sense," Bukhari said. "He's dedicated his whole life on that cause."