The clip, which was posted on YouTube last week, is headlined "Austin Tice still alive," McClatchy Newspapers reported. A link to the clip appeared Monday on a website supporting Syrian President Bashar Assad.
Tice, 31, a former U.S. Marine, was last heard from Aug. 13 when he was believed to be in a Damascus suburb. He failed to appear at a rendezvous with friends in Lebanon a few days later.
Victoria Nuland, a State Department spokeswoman, said officials believe Tice is being held by the Syrian government.
The video clip shows Tice surrounded by bearded men wearing baggy clothes like those of Afghan fighters. Tice attempts to say a Muslim prayer, concluding "Oh, Jesus," while the men around him say "God is great."
"Knowing Austin is alive and well is comforting to our family," Tice's parents, Marc and Debra Tice of Houston, said in a statement. "Though it is difficult to see our eldest son in such a setting and situation as that depicted in the video, it is reassuring that he appears to be unharmed."
Tice's stories and photographs from Syria were used by The Washington Post and other news organizations.