The parents of an American journalist kidnapped in Syria six years ago appealed on Tuesday for the United States and Syria to work together to find their son and said they had applied for Syrian visas to lobby there for his release.

Austin Tice was 31 years old when he was detained in August 2012 at a checkpoint while reporting in Damascus on the uprising against Syrian President Bashar Assad.

He has not been heard from publicly since a video posted online weeks after he disappeared showed him in the custody of armed men, though both Washington and his parents say they believe he is alive.