Former US defense secretary Robert Gates on Sunday endorsed the idea of having a special court review drone strikes as a check against a president's power to, in effect, execute Americans.
The issue came to the fore last week during a Senate hearing to confirm John Brennan, President Barack Obama's counter-terrorism chief, as director of the CIA.
Gates, a former CIA director who served as defense secretary under both Obama and former president George W. Bush, said the rules followed by the Obama administration "are quite stringent and are not being abused."
"But who is to say about a future president?" he said in an interview with CNN's State of the Union.
"I just think some check on the ability of a president to do this has merit as we look to the longer-term future," he said.
Gates referred to the targeted killings as "being able to execute in effect an American citizen, no matter how awful," and said some third party should have a say in it, with the intelligence committees of Congress kept informed.
He noted that there is already a foreign intelligence surveillance court that approves the use of electronic surveillance of American citizens, and something similar could be created to review targeted killings of Americans.
"Something that would give the American people confidence that there was, in fact, a compelling case to launch an attack against an American citizen," he said.
During Thursday's confirmation hearing, Senator Dianne Feinstein said she would introduce legislation to create such a court to review drone strikes.
Missiles fired from unmanned aircraft have become the administration's weapon of choice in its secret war against suspected Al-Qaeda plotters.
The administration's legal rationale for the targeted killings were leaked to the media ahead the Senate hearings.
It allows the use of drone strikes against US citizens suspected of being senior Al-Qaeda operatives, even if there is no evidence they are actively plotting an attack.
Among the most controversial drone strikes were the September 2011 killings in Yemen of Anwar al-Awlaki and Samir Khan, whose deaths stoked concern because they were US citizens who had never been charged with a crime.