An American aid worker kidnapped last year by al-Qaeda militants in Pakistan has made an impassioned video appeal to US president Barack Obama to save his life.  Warren Weinstein, 70, abducted from his home by gunmen in the eastern city of Lahore in August, begged Obama to meet his captors\' demands in the video released by al-Qaeda\'s media arm — the first footage of Weinstein to surface since his capture. The video — on which the recording date was unclear — followed an audio recording released in December in which al-Qaeda chief Ayman al-Zawahri acknowledged holding Weinstein and demanded that the United States end airstrikes against his group and release its prisoners being held in American jails. Among those held is Khalid Sheik Mohammed, who was arraigned at the Guantanamo Bay detention centre Saturday along with four other defendants accused of orchestrating the September 11, 2001, terrorist attacks. In Washington, White House spokesperson Jay Carney said that the White House was \"greatly concerned for Mr Weinstein\'s safety and his well-being\" and called for his immediate release, but he said, \"We cannot and will not negotiate with al-Qaeda.\" Humanitarian work in Pakistan has been rocked by a series of kidnappings, including the beheading last month of a British aid worker in the western city of Quetta, who was presumed also to have been in the hands of Islamic extremists. Though the abductions often have ideological motives, they are also a means for Pakistani militants to raise money.