U.S. officials say they will not negotiate with al-Qaida over the fate of a 70-year-old American aid worker held hostage in Pakistan, despite the man's video plea for help from President Barack Obama.

White House spokesman Jay Carney said Monday that Washington “cannot and will not” negotiate with al-Qaida, but that there is great concern about Warren Weinstein's safety. He added that U.S. officials are working to locate Weinstein, who was abducted nine months ago in Pakistan.

A video message from Weinstein that appeared online Sunday on jihadist forums reportedly was posted by al-Qaida's media wing. Weinstein addresses President Obama in the nearly three-minute-long video, saying his captors will kill him if their demands for an end to U.S. airstrikes and the release of prisoners are not met.

Weinstein wore a traditional tunic of the Pakistani-Afghan region and sat at a table with books and food. Although he suffers from heart problems, the American told his wife he is in good health.

It is unclear when the message was recorded.

Last December, al-Qaida chief Ayman al-Zawahiri said in an online video that Weinstein would not be released until the United States ends its airstrikes in Muslim countries. He also demanded the release of al-Qaida and Taliban prisoners.

Eight gunmen seized Weinstein at his home in Lahore, Pakistan, last year just days before he was scheduled to return to the United States. He was serving as director in Pakistan of a private U.S.-based development consulting company, J.E. Austin Associates.