US fears Iran's links to Al Qaeda as officials believe country may have provided aid to terror group

The men, who were detained in Iran in 2003, make up Al Qaeda's so-called management council, a group that includes members of the inner circle that advised Usama bin Laden and an explosives expert widely considered a candidate for a top post in the organization.

The assertions are likely to amplify tensions between Washington and Tehran. A U.S. Senate committee on Thursday moved to intensify sanctions to force Iran into negotiations on its nuclear program, while Tehran has largely defied pressure. This week, Iran prevented UN nuclear inspectors from gaining access to sites and scientists, according to diplomats.

Skeptics caution that intelligence on Iran's activities is limited and worry that some policy makers might use provocative reports to justify military action against Tehran. Iran has denied any connection with Al Qaeda.

U.S. officials believe there have been recent indications that officials in the Iranian government have provided Al Qaeda operatives in Iran limited assistance, including logistical help, money and cars, according to a person briefed on the developments.

Adding to the U.S. pressure on Iran, Director of National Intelligence James Clapper told senators in an annual intelligence assessment that U.S. agencies believe the Iranian regime is now more willing to conduct an attack in the U.S.

"We have to be vigilant for more of that," Clapper told lawmakers Thursday.

The reports come at a time of growing concern about Iran's decision-making. President Barack Obama, in his recent State of the Union address, said, "America is determined to prevent Iran from getting a nuclear weapon, and I will take no options off the table to achieve that goal."