Biden calls on Syria to help secure release of journalist Austin Tice

"We know with certainty that he has been held by the Syrian regime," Biden said in a statement. "We have repeatedly asked the government of Syria to work with us so that we can bring Austin home.

"On the tenth anniversary of his abduction, I am calling on Syria to end this and help us bring him home," he said.

Biden said Tice, a former US Marine turned journalist, "put the truth above himself and traveled to Syria to show the world the real cost of war."

"There is no higher priority in my administration than the recovery and return of Americans held hostage or wrongfully detained abroad," Biden said.

"That is a pledge I have made to the American people and to Austin's parents, and it is one that I am determined to uphold," he added.

Tice was a freelance photojournalist working for Agence France-Presse, McClatchy News, The Washington Post, CBS and other news organizations when he disappeared after being detained at a checkpoint near Damascus on August 14, 2012.

Thirty-one years old at the time he was captured, Tice appeared blindfolded in the custody of an unidentified group of armed men in a video a month later but there has been little news since.