WASHINGTON — The parents of an American reporter held captive in Syria for more than two years are asking Americans to sign an online petition urging the U.S. government to step up its efforts to get him home and to post photographs of themselves symbolically blindfolded.

The publicity campaign on behalf of Austin Tice, a freelance journalist whose work was published in The Washington Post and McClatchy Newspapers, is being coordinated by his parents, Marc and Debra Tice of Houston, and the advocacy group Reporters Without Borders.

Although Tice’s whereabouts are unknown, his parents remain convinced that he is still alive.

Delphine Halgand, the U.S. director for the France-based Reporters Without Borders, said ads directing readers to FreeAustinTice.rsf.org will run on the websites of more than 260 news organizations around the country. The Washington Post will be among them, said Executive Editor Marty Baron.

“We’re heartened at the enormous support Austin is receiving,” Baron said in a statement. “We want to do everything we can to raise awareness of his horrifyingly long captivity and to facilitate his release.”

The petition, addressed to President Obama, notes Tice was abducted in August 2012 in Syria, the world’s most dangerous war zone for reporters. The petition asks that Obama “do all you can to bring him safely home.”

Supporters also are asked to take photographs of themselves in a gesture of support, with a black cloth tied over their eyes.

“When a journalist is kidnapped we all are blindfolded because we are deprived of information,” said Halgand.

The imagery also recalls wrenching images of Tice on the one sighting of him since his capture. An undated YouTube video showed him blindfolded as he stumbled down a hilltop surrounded by armed men.

The circumstances in which Tice, 33, was abducted are unclear. His parents say they have made inquiries through the Syrian government, not any militant groups.

“Austin is suspended between two governments,” Marc Tice said in a telephone interview. “The Syrian government has told us they will do what they can to locate and return Austin safely. And the American government says they’re doing everything they can. We think dialogue and collaboration, communication between these governments could very well be useful.”

The Tices also have been talking with White House officials conducting a review of U.S. hostage policy, though the administration has made clear there will be no change in the policy of refusing to pay ransoms for hostages.

Marc Tice said he and his wife do not favor a rescue attempt to get their son out of Syria.

“We’re not looking at putting American soldiers in harm’s way to try to save Austin,” he said. “We believe in diplomacy, dialogue, in communication between the two countries.”

One other American journalist besides Tice is still being held in Syria. Kevin Dawes, a freelance photographer, has been missing since October of 2012. He is not believed to be among the hostages being held by the Islamic State.