Al-Qaeda leader Ayman al-Zawahiri claimed in a new recorded message released Thursday that the terrorist group is holding an American aid worker hostage in Pakistan, an assertion that U.S. intelligence officials said was credible.

The message marked the first time that al-Qaeda has asserted responsibility for the kidnapping of Warren Weinstein, the 70-year-old Pakistan director for an Arlington County-based development contractor. He was abducted in August at gunpoint from his residence in Lahore.

U.S. officials said that recent intelligence has indicated that al-Qaeda has expressed interest in kidnapping plots but added that they had no direct evidence that al-Qaeda was holding Weinstein.

“It’s entirely possible that al-Qaeda or one of its militant allies may be holding Mr. Weinstein, and the statement by Zawahiri supports this conclusion,” said a U.S. official, who spoke on the condition of anonymity because of the sensitivity of the matter. “The U.S. government is following every lead to help find Mr. Weinstein.”

A U.S. counterterrorism official noted that al-Qaeda typically does not make false claims about kidnappings or other operations. “We’ve never seen a bogus one,” the official said.

The recorded message comes as the network has lost all but two of its top leaders, putting Zawahiri under significant pressure to find a way to rebuild the organization and reassert its relevance in Pakistan.

In the statement, Zawahiri referred to the treatment of al-Qaeda suspects in U.S. custody and said that Weinstein has not been tortured.

“Just as the Americans detain all whom they suspect of links to al-Qaeda and the Taliban, even remotely, we detained this man who is neck-deep in American aid to Pakistan since the ’70s,” Zawahiri said, according to a translation by the Site Intelligence Group.

Zawahiri also listed demands for Weinstein’s release, calling for an end to airstrikes in Afghanistan, Pakistan, Somalia and Yemen as well as the release of Muslim prisoners — including Omar Abdul Rahman, the “blind sheik” who was convicted of conspiracy charges in connection with the 1993 attack on the World Trade Center.

Zawahiri also demanded the release of the family of Osama bin Laden, who was killed in a U.S. commando raid in Abbottabad, Pakistan, in May. Bin Laden’s wives were briefly questioned by U.S. special operations troops and then taken into custody by Pakistani authorities.

U.S. officials acknowledged that they have little information on Weinstein’s whereabouts, adding that it is unclear whether he has been moved from Lahore into the tribal territories of Pakista, where Zawahiri is believed to be in hiding.

The officials also they did not know whether al-Qaeda captured Weinstein or whether he was taken prisoner by another group. Lesser-known militant organizations in Afghanistan and Pakistan have frequently taken prisoners who were passed along to other organizations, often for payment.

Weinstein worked in Pakistan for J.E. Austin Associates, a consulting firm that manages development projects. He was previously a career official with the U.S. Agency for International Development.

The Austin firm has carried out numerous projects for USAID in Pakistan over the years, primarily related to business and trade development. Weinstein worked on small-business development.

“He did work on various private-sector development projects,” primarily with small private-sector export businesses including jewelry-making and marble, said an administration official who worked with Weinstein in Pakistan. “He’d been there a number of years. He is a sweet guy and really loved the place.”

Zawahiri’s message also included an acknowledgment that the terrorist group’s former operational leader, Atiyah Abd al-Rahman,, had been killed in a U.S. drone strike in August.

“The retaliation, with permission from Allah, will be taken against those Crusader Westerners who killed him and his two sons,” Zawahiri said.

Staff writer Karen DeYoung and staff researcher Julie Tate contributed to this report.