Investigators determined that the video was routed through an Internet address in Pakistan, suggesting that Levinson might be held there. Also, Pashtun wedding music played faintly in the background, officials said. The Pashtun people live primarily in Pakistan and Afghanistan, just over Iran's eastern border.

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The photos, however, traced back to a different Internet address, this one in Afghanistan.

Authorities don't know whether those clues mean Levinson was being held in Balochistan - a rugged, arid region that spans parts of Iran, Pakistan and Afghanistan - or perhaps in the lawless tribal region along the border of Pakistan and Afghanistan. These areas are home to terrorists, militant groups and criminal organizations.

None of these groups has a clear motive for picking up Levinson. But an American hostage, particularly one who used to work for the U.S. government, would be considered a valuable commodity to any of them.

Over the past year, the hopefulness that initially followed the arrival of the video has faded. The meetings with the Iranians have not provided a breakthrough and U.S. officials said the government was no longer as optimistic about the future of those talks.

"We don't know what else to do," David Levinson says in the video released Friday. "Please tell us what you want."

Some U.S. officials believe the Iranian government routed the video through Pakistan as a way to blame Levinson's disappearance on someone else - most likely the anti-Iran terrorist group Jundallah. But as with every other possibility, the U.S. has no proof.

The video was accompanied by a demand that the U.S. release prisoners, but officials said the United States is not holding anyone matching the names on the list. It's possible some of them may have been held by the Pakistani government at one point, but officials say the demand doesn't offer any indication of who might be holding Levinson and there's been no more communication about it.

U.S. authorities have repeatedly analyzed the video and the apparently scripted remarks Levinson made, looking for clues.

For instance, Levinson said a "group" had held him for three and a half years, a word choice that could suggest a criminal organization or terrorist group, rather than a government. And he said he had been held "here" for that time, suggesting he had not been moved.

Levinson's dire warning about his diabetes medication is perplexing. He vanished years ago. Whoever is holding him must have had access to diabetes medicine at one point. Was he running out of medication because he was moved somewhere else? Or was it simply intended to add even more urgency for the U.S.?

Relations with Iran, meanwhile, have worsened. The Justice Department recently accused Iranian intelligence agents of plotting to assassinate Saudi Arabia's ambassador in Washington. Then a United Nations watchdog released a report warning of Iran's nuclear ambitions, prompting the United States and its Western allies to issue new sanctions against Iran's financial system.

Most recently, a high-tech, stealth CIA drone was captured by Iranian officials while on a surveillance mission over Iran. The embarrassing mishap put sophisticated technology in Iranian hands and provided public evidence of the kind of spying that's been long suspected.

The one bright spot in Washington's relationship with Tehran was the release of two American hikers from an Iranian prison in September. The U.S. worked behind the scenes to secure that release but officials said Levinson was not part of those discussions.

"All I want is for our family to be whole again," Christine Levinson said in the video, in a message directed toward her husband. "We love you. We miss you every day. We will not abandon you."