Al-Qaida claimed responsibility Thursday for the kidnapping of a 70-year-old American aid worker in Pakistan in August, and issued a series of demands for his release.

In a video message posted on militant websites, al-Qaida leader Ayman al-Zawahri said Warren Weinstein would be released if the United States stopped airstrikes in Afghanistan, Pakistan, Somalia and Yemen. He also demanded the release of all al-Qaida and Taliban suspects around the world.

"Just as the Americans detain all whom they suspect of links to al-Qaida and the Taliban, even remotely, we detained this man who is neck-deep in American aid to Pakistan since the 1970s," al-Zawahri said, according to a translation provided by the SITE Intelligence Group, which monitors militant messages.

Weinstein was abducted by armed men from his house in the eastern city of Lahore on Aug. 13. Police and U.S. officials have not publicly said who they believed was holding him, but Islamist militant groups were the main suspects.

Weinstein, who has a home in Rockville, Maryland, worked in Pakistan for several years and spoke Urdu.

He was the country director in Pakistan for J.E. Austin Associates, a U.S.-based firm that advises a range of Pakistani business and government sectors. The company has said Weinstein is in poor health and provided a detailed list of medications, many of them for heart problems, that it implored the kidnappers to give him.