The US believe that missing former FBI agent Robert Levinson is no longer in Iran, the White House said.
White House spokesman Josh Earnest did not explain what led Washington to the assessment, but said on Tuesday that "we continue to press for information about his whereabouts", Xinhua reported.
The US has secured a commitment from Iran to help locate Levinson, vowing that "we're going to hold the Iranians to that commitment", he said.
Levinson went missing on Iran's Kish Island in 2007. Press reports said he was paid by the US intelligence agency to gather intelligence inside Iran, while Tehran has repeatedly denied it was holding the American.
Levinson was not among the five Americans released by Tehran over the weekend as part of a prisoner swap with Washington.
"We are happy for the other families. But once again, Bob Levinson has been left behind. We are devastated," Levinson's family said.