Top U.S. officials say they strongly believe American reporter Austin Tice, missing in Syria for more than six years, is still alive.
State Department special envoy for hostage affairs, Robert O'Brien, would not talk about the intelligence that led him to make that assessment. But he told reporters the department is leading a multinational effort to find Tice and get him freed.
O'Brien appealed to Russia, Syria's closest ally, for help.
"There are plenty of disagreements between the United States and Russia at this time. One of the things that Russia and the United States should agree on is that innocent Americans, or innocent Russians ... should not be held hostage and should not be held against their will."
The FBI is offering a $1 million reward for information leading to his safe return.
Tice is a former U.S. Marine captain who turned to journalism. He disappeared in Syria in August 2012 shortly after the civil war erupted.
He appeared in a video a month later, blindfolded and surrounded by armed militants.
It is unclear who is holding him.