President Barack Obama’s deadly drone war against suspected extremists, including Americans overseas, may not be legal, Sen. Bob Corker, the top Republican on the Senate Foreign Relations Committee, told Yahoo News in an exclusive interview. And, Corker said, the drone campaign may be creating more terrorists than it is killing.

The Tennessee lawmaker told Yahoo News Thursday afternoon that Obama should wait until after Afghanistan’s April 2014 elections to decide on the pace of U.S. troop withdrawal there. Corker also bluntly declared that he does not trust Afghan President Hamid Karzai and vowed to make sure the State Department carries out reforms proposed in response to the deadly terrorist attack against the U.S. compound in Benghazi, Libya, last September.

The hour-long interview in Corker’s tidy Capitol Hill office came as the Senate Intelligence Committee grilled Obama’s nominee to head the CIA, John Brennan, over his role in expanding America’s controversial drone campaign.

The White House sometimes seems to regard Brennan “to be this priestly figure who goes to work every day in a windowless room and decides who he’s going to execute that day,” Corker said. “That’s got to be offensive to American values.”

He added, “I think it would be very helpful to the administration, and to the American people, but certainly the world, for us to develop a policy that’s a lot different" than one that places Brennan in such a role.

Is the drone campaign legal?

“I don’t know,” Corker said, noting that he had not yet been able to see Justice Department memos laying out the broad legal justification for deadly strikes that sometimes target U.S. citizens overseas. “Even the most hawkish American has to have some degree of concern” about the policy, he said.

Drone strikes arouse deep public anger, notably in countries with large Muslim populations—much as the Iraq War did. A formal 2006 study by America’s intelligence community found that the Iraq invasion and occupation was creating terrorists faster than U.S. forces could take them out. Could the same thing be happening with drones?

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“It could well be doing that,” Corker said. “I’ve been to Pakistan three times, that’s something that they continue to bring up. It’s very understandable.”

Corker stressed that the U.S. needs to be mindful that a day will come “very soon” when other countries have the technology to carry out their own unmanned aerial vehicle strikes. Washington should adopt a system of rules now that could set an example, he said.

“We’ve got to have a set of standards, and checks and balances that help ferret out the ethical issues that need to be ferreted out because soon other countries are going to be doing the same thing,” Corker said.

While some of his colleagues focus single-mindedly on the number of U.S. troops as the key to success in Afghanistan, Corker emphasized the importance of that country's next elections, set for April 2014.

“The biggest factor in the success of Afghanistan likely is to be the elections, and how that’s handled, and who’s elected, and the process,” he said. “I don’t understand why a decision has to be made now as to the number of troops.

“We could wait and decide how many troops are going to be on the ground,” Corker said. “But our allies are really—really worried—worried about us making a decision that really takes us to levels that allow the gains that have been put forth to dissipate.”

Should the U.S. trust Karzai? “No,” Corker said without hesitation. “I have never trusted Karzai ... He’s certainly got some strengths, but no, I don’t trust him.”

On Iran, Corker predicted Congress would push ahead with a fresh round of sanctions even as the Obama administration pursues negotiations meant to get Tehran to freeze its suspected nuclear program. But that diplomatic outreach may also be laying the groundwork in the event that talks fail and Obama decides to use military force, Corker said.

"The more we are out there diplomatically, doing everything we can to, in a rational way, negotiate with the Iranians, I do think we are building world support should something else have to occur," Corker said.

On the Benghazi attack, which killed Ambassador Chris Stevens and three other Americans, the senator noted that the State Department was a "sclerotic" bureaucracy. The Foreign Relations Committee should keep the pressure on to ensure the implementation of a report recommending a series of reforms, Corker said.

"We definitely need to make sure that it gets seen through," he said.

Corker is a staunch conservative but no fire-breather—he was one of just three Republicans to back ratification of the new START nuclear arms control treaty with Russia. He says he did so after securing an Obama administration commitment to modernize the existing arsenal as well as to test and monitor facilities. But now, he says, the president will find future arms control treaties a heavier lift in Congress.

“The modernization hasn’t happened,” he said. “There’s a little bit of a trust issue there” that would be “detrimental” to future ratification efforts.

With Foreign Relations Committee Chairman Bob Menendez facing a mounting scandal, Corker declined to say whether the New Jersey Democrat's woes would affect the committee’s work.

“I’ve had zero involvement,” Corker said. “It’s hard for me to discern the serious, the non-seriousness” of the allegations.

At another point, however, Corker described his embattled colleague as "the driver of the agenda" in the committee.

How did Corker, a Tennessee shopping-center builder and real estate investor, develop such an interest in foreign affairs? Corker traces his interest back to a trip to Haiti when he was in his 20s, organized by his church. He went along as an expert in construction—but came back eager to help his home state. After serving there in a variety of capacities—notably mayor of Chattanooga—Corker won election to the Senate in a bitter 2006 battle. “I had a significant economic experience,” he said. “But I knew one of my weaknesses, big weaknesses, was foreign relations.”