Defense Secretary Ash Carter said Thursday that the two U.S. Navy boats seized by the Iranian military had strayed accidentally into Iran's waters due to a "navigation error."
"It does appear ... that they did stray accidentally into Iranian waters due to a navigation error, so that seems to be the original cause of this," he said in an interview with Univision.
Carter also said it was "not abnormal" for the Iranian military to board the U.S. boats because they were in Iran's waters.
Iranian state news media released photos and videos showing the U.S. sailors — one woman and nine men — kneeling with their hands behind their heads. One video showed a U.S. sailor apologizing and calling it a mistake, but it is not clear whether it was recorded under duress.
Carter said "we need to wait and see what the full context of that is" but said the U.S. would not have done the same in Iran's position.
"By the way, that's not something we would have done," he said.
Republican critics have slammed the administration for framing the incident as a positive example of diplomacy and highlighting that the Americans were not held for as long as British sailors were in a similar 2007 incident.
Asked whether the sailor actually apologized, Carter said, there was "no indication that our sailors did anything except indicate what they knew. ... It clearly was a mistake."
Officials have been revealing more details about the incident since the 10 sailors were debriefed after their release Wednesday.