Al-Qaida told the family of a US hostage kidnapped three years ago in Pakistan to press their government to exchange him for prisoners held by the United States, in a message posted on the Internet on Friday.
Warren Weinstein, who was kidnapped in 2011 in Lahore where he worked for a US consulting company, was last seen in a video recording released in December.
In the latest message, al-Qaida said it had been demanding to exchange Weinstein for members of the group held by the United States for "no guilt except that they acted in defense of the Muslim ummah (nation)" - an apparent reference to inmates held at the US military base in Guantanamo Bay in Cuba.
"Your government wants Warren Weinstein to die in prison so that it may absolve itself of responsibility regarding his case," the message said. "Your government has not made any serious effort for the release of the prisoner."
Addressing the Weinstein family, it said the US government's failure to negotiate "will only lead to your prisoner dying a lonely death in prison".
"Therefore, if you want Warren Weinstein to be released, do whatever you can to pressurize your government."
It was not immediately possible to verify the authenticity of the message which was posted on a website that has been used by radical Islamists for similar announcements in the past.
In a 13-minute video clip posted on the Internet in December 2013, Weinstein looked gaunt and tired as he appealed to President Barack Obama to intervene to negotiate his freedom.
Pakistan's tribal areas on its border with Afghanistan serve as safe havens for al Qaeda, the Taliban and other militant groups.