Story highlights The 10 U.S. Navy sailors captured by Iranians were told to "act happy" for a videotaped apology

A U.S. official said there was no evidence of physical harm to the sailors but the demand to "act happy" is a sign of potential mental duress

Washington (CNN) The 10 U.S. Navy sailors held by Iran were told by their captors to "act happy" while they were being videotaped during their detention, according to a U.S. defense official with access to the latest information about the debriefing of the sailors.

The U.S. commander who spoke on camera has indicated he felt pressure to talk about how well they were being treated. It's not yet clear if he was directly ordered to apologize, the official said.

The U.S sailor was filmed saying, "It was a mistake that was our fault and we apologize for our mistake."

While the nine men and one woman sailor were not physically mistreated, the information from the defense official was the first indication they were under some direct mental duress from the Iranians.

The Iranian state-run TV footage of the sailors being captured, on their knees with their hands behind their heads, and a subsequent video of one sailor apologizing has been fodder for Republican critics of President Barack Obama since the news first hit just hours before his final State of the Union. The latest details could further fan the flames.

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