The pressure comes after revelations that the CIA is planning to use drones to assassinate a US citizen accused by the White House of plotting attack against Americans overseas.
Legal experts and civil liberties are pressing the Obama administration to explain the basis for a potential strike against the suspect.
According to the Associated Press, senior US officials are weighing the benefits of assassinating the man, who has not yet been charged with a crime.
The United States has adopted a drone policy, since 2004, to target “suspected militants” in countries like Pakistan, Afghanistan and Libya, among others. Local and international reports, however, show the main victims of the American drone campaign have been civilians.
The White House “continues to fight against even basic transparency” about how it justifies the executions of thousands of people under the program, said Hina Shamsi, the director of the American Civil Liberties Union’s (ACLU) National Security Project.
“The targeted killing of an American being considered right now shows the inherent danger of a killing program based on vague and shifting legal standards, which has made it disturbingly easy for the government to operate outside the law,” she said.
Citing several US officials, the AP reported that the suspect is hiding, well guarded, in a remote part of Libya, which is unwilling to allow US operations on its soil and “unable to go after him.”
According to the report, one US official said that the Pentagon did ultimately decide to recommend lethal action against the suspect.
The US Justice Department has not yet built a formal case against the man.