"I can tell you flatly that U.S. forces are not operating across the Iraqi border into Iran," Crocker said in an interview on CNN's "Late Edition" program.

Ryan made the comments in reaction to a report published Sunday in The New Yorker magazine that the Bush administration has been conducting covert military actions against Iran.

The article by Seymour Hersh is based on a classified Presidential Finding signed by President George W. Bush. Hersh said he did not disbelieve Crocker when he said he knows of no military actions against the Islamic republic.

"Sometimes it's better not to have the ambassador know. He may not know the extent to which we're operating deeply inside Iran," Hersh said.