President Bush says allegations that Iran's president-elect played a key role in the 1979 Tehran hostage crisis raise many questions.
The president told reporters Thursday he has no further information about the allegations, but said he is confident that questions about Mahmoud Ahmadinejad's possible role in the incident will be answered.
The State Department said Tehran has an obligation to speak definitively about the matter.
Mr. Ahmadinejad, who was in his early 20's at the time, has not publicly addressed the allegations, but his allies have denied them.
Several former American hostages described Mr. Ahmadinejad as "a cruel individual" who interrogated them. But other hostages say they don't remember him.
A group of radical Iranian students stormed the U.S. embassy in Tehran in November 1979 and held 52 Americans hostage for 444 days.
Some information for this report provided by Reuters, AFP and AP.