The lawyer for Dr Shakil Afridi, who helped CIA track slain al-Qaeda leader Osama bin Laden to his hideout in Abbottabad in 2011, has quit the case after receiving a number of death threats.
Lawyer Samiullah Afridi told the BBC that the US pressure on Pakistan for the release of Afridi was another reason for his decision.
Dr Afridi is accused of using the cover of a door-to-door vaccination campaign to help the US find Osama.
Samiullah Afridi said that his life had been under threat since he took up the case two years ago.
According to the report, Afridi, who is not related to Dr Afridi, said he had left the country at one point because of safety fears.
Afridi added that he took the case on humanitarian grounds, but now he will have to look for his own life, as it was more important.
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He said that Washington's continued refusal to release Dr Aafia Siddiqui - a US citizen of Pakistani origin jailed for alleged links to al-Qaeda - was also 'creating hurdles,' the report said.
Afridi, one of four lawyers representing the doctor, said he had 'no option' but to quit the case.