Al-Qaida kidnappers in Pakistan have released a video of a captured American consultant, looking frail and appealing for help from Barack Obama.

Warren Weinstein, 72, was seized two years ago while advising the Pakistani government on economic development and his captors have said they would only release him if the US stops all air strikes and releases terrorist suspects around the world.

Within hours of the film's release, Pakistani intelligence officials said a suspected American drone had fired two missiles at a home in the northwestern tribal region bordering Afghanistan, killing at least three foreign militants.

It was unclear which came first however. Associated Press reported the latest drone strike took place just before midnight Wednesday in the village of Qutab Khel in North Waziristan and was successfully targeted at Arab militants operating in the area.

The video of Weinstein was released to Pakistani reporters on Christmas Day but first appeared in US media on Thursday.

"The years have taken their toll," Weinstein says in the 13-minute video, which describes how he is not in good health and suffers from acute asthma.

Appearing to read from a statement, he adds: "Nine years ago, I came to Pakistan to help my government and I did so at a time when most Americans would not come here," he said. "And now, when I need my government, it seems I have been totally abandoned and forgotten."

The former New York state university professor also appears to make a direct appeal to the US president.

"Mr Obama, you're a family man," Weinstein is seen to say. "You understand the deep mental anxiety and anguish that I have been experiencing for these past more than two years. And therefore I'm appealing to you on a humanitarian basis, if nothing else, and asking that you take the necessary actions to expedite my release and my return to my family and to my country."

The video is the third apparently released by his captors since Weinstein was taken on August 13, 2011 from his home in Lahore.

The US state department in Washington said it was still trying to verify the video and a separate letter purporting to be from Weinstein, but repeated its demands for his immediate and unconditional release.

“We're working hard to authenticate this latest report, but we reiterate our call that Warren Weinstein be released and returned to his family,” said spokeswoman Jen Psaki. “Particularly during this holiday season – another one away from his family – our hopes and prayers are with him and those who love and miss him."

Weinstein, who has a home in Maryland, was country director in Pakistan for JE Austin Associates, a US-based firm that advises Pakistani businesses and government departments.

Earlier videos released in September 2012 showed Weinstein appealing for help from the Jewish community and Israel's prime minister.