WASHINGTON – A moderate Republican senator, vital to any White House hopes of getting U.N. Ambassador Susan Rice confirmed as secretary of state, said Wednesday she couldn't back any nomination until more questions are answered about the deadly Sept. 11 attack in Libya and Rice's State Department role during the 1998 U.S. Embassy bombing in Kenya.

In a fresh suggestion of eroding GOP support for Rice, Sen. Susan Collins of Maine emerged from a 90-minute, closed-door meeting with the ambassador voicing new criticism of her initial account about Libya. Collins also questioned what Rice, the assistant secretary of state for African Affairs in the Clinton administration, knew about requests for enhanced embassy security before the Nairobi truck bombing.

Pressed on how she would vote if President Barack Obama names Rice to succeed Secretary of State Hillary Rodham Clinton, Collins said, "I would need to have additional information before I could support her nomination."