Washington (CNN) - The number of innocent victims of drone strikes remains "extremely small" and doesn't outweigh the benefits of using drones to take out al Qaeda operatives, former Defense Secretary Robert Gates argued Sunday.
But the former Pentagon chief said a better system of checks and balances could be constructive when the unmanned aerial devices are used to target Americans, aligning himself with lawmakers concerned about unfettered power in the hands of the president.
"I think some check on the ability of the president to do this has merit, as we look to the longer term future," Gates told CNN chief political correspondent Candy Crowley on "State of the Union."
Gates served under George W. Bush during the beginnings of the drone program and later under President Barack Obama as the use of drones spiked. Recently lawmakers, both Democrats and Republicans, have forcefully questioned the use and oversight of the lethal devices.
"I'm a big advocate of drones," Gates said, detailing how as CIA director under Bush, he pressed for ramping up the use of drones to monitor and target suspected terrorists.
While innocent people are killed by drones, "the numbers, I believe are extremely small," Gates said. "You do have the ability to limit that collateral damage more than with any other weapons system that you have."
The New America Foundation estimates that in Pakistan, between 1,953 and 3,279 people have been killed by drones since 2004 - and that between 18% and 23% of them were not militants. The nonmilitant casualty rate was down to about 10% in 2012, the group says.
In Yemen, the group estimates, between 646 and 928 people have been killed in a combination of drone strikes and airstrikes, and 623 to 860 of those killed were militants. Only about 2% of those killed have been high-level targets, the group said.
Gates' remarks came as the U.S. Senate considers the nomination of John Brennan to become the next CIA director. As Obama's chief counterterrorism adviser, Brennan was a vocal advocate for using drones to target America's enemies.
Some lawmakers, along with human rights organizations and civil libertarians, have questioned the oversight procedures dictating the use of drones, particularly when they're used to target American citizens overseas. That was the case when New Mexico-born Anwar al-Awlaki - who officials said played an operational role in al Qaeda in the Arabian Peninsula - was killed by a U.S. drone in 2011.
On Sunday, two senators decried the system currently used for deciding when to use drones to take out Americans overseas, saying it was a constitutional violation that demanded reform.
"It's very unseemly that a politician gets to decide the death of an American citizen," Sen. Rand Paul, R-Kentucky, said on CNN.
"There needs to be a trial for treason. The president, or a politician, Republican or Democrat, should never get to decide someone's death by flipping through flash cards," Paul continued.
"I don't know how often this will happen, but I agree with Rand Paul," said Angus King, the independent senator from Maine. He was elected in November and caucuses with the Democrats.
"The Fifth Amendment says that no person shall denied life, liberty or pursuit of happiness. These may be Americans that have committed treason by signing up with another country or another group against us, but it just makes me uncomfortable that the president, whoever it is, is the prosecutor, the judge, the jury, and the executioner, all rolled into one," he continued.
What's needed, King argued, is a check on the president's power that would retain the ability to order stealth surveillance and rapid action.
"Where there is time, go in, submit it to a third party, a court, in confidence, and get a judgment that there is sufficient evidence," King said. "Some say these people should have a whole trial. I don't believe that. But I think some independent check on the executive is healthy for our system."
That type of independent body should be considered, Gates said, if it gave Americans confidence the government was acting in good faith.
"Whether it's a panel of three judges or one judge or something that would give the American people confidence that there was, in fact, a compelling case to launch an attack against an American citizen - I think just as an independent confirmation or affirmation, if you will - is something worth giving serious consideration to," he said.
In hearings last week on Brennan's nomination to head the CIA, Senate Intelligence Committee Chairwoman Dianne Feinstein said she would review ideas for legislation "to ensure that drone strikes are carried out in a manner consistent with our values," including a proposal to create a body that would review such strikes.
However, the intelligence panel has yet to begin drafting legislation, a Feinstein aide told CNN. For now, the panel is reading through proposals and suggestions by experts and commentators.
According to the aide, who spoke on condition of not being identified, writing a bill raised "a lot of questions to wrestle with." Consultations with the Judiciary and Armed Services Committees as well as the White House must occur before a final proposal can be developed, the aide added.
CNN's Pam Benson and Josh Levs contributed to this report.