WASHINGTON (CNN) -- Sen. John Kerry, the president's nominee for secretary of state, put America's anxiety over Iran front and center during his confirmation hearing, saying the "questions surrounding Iran's nuclear program" must be resolved.
"The president has made it definitive," Kerry told the Senate Foreign Relations Committee Thursday during what is expected to be an easy confirmation process.
"We will do what we must do to prevent Iran from obtaining a nuclear weapon, and I repeat here today, our policy is not containment. It is prevention, and the clock is ticking on our efforts to secure responsible compliance."
There are sanctions and they are working, he said, noting Iran's currency, the rial, has dropped, and other nations have been cooperating in reducing dependence on Iranian oil.
He said there is hope that progress can be made on the diplomatic front with Iran, which says its nuclear aspirations are solely peaceful. World powers believe Iran wants to build nuclear weapons.
"Iranians need to understand that there's no other agenda here," he said. "If their program is peaceful, they can prove it. And that's what we are seeking."
The longtime Massachusetts senator was asked about and addressed a wide range of issues before the committee, a panel he chaired for the past four years.
Regarding the Arab Spring, he cited the self-immolation of a Tunisian fruit vendor that triggered the first uprising and the revolt in Cairo's Tahrir Square as examples of ferment.
The major social cause, he said: "Burgeoning populations of young people hungry for jobs, opportunity, individual rights, and freedom are rebelling against years of disenfranchisement and humiliation."
He said Syria and its president, Bashar al-Assad -- now embroiled in civil war -- was well aware of Syria's youthful population and knew he needed to adjust to it.
"I remember president Assad said to me, 'I have 500,000 kids who turn 18 every year, and I don't have a place to put them. I don't have jobs. I need to be able to change what's happening here.' And, you know, clearly thinking down the road, you know, he wanted to try to find some way to reach out to the West and see if there was some kind of accommodation," Kerry said.
"That never happened. And it's now moot, because he has made a set of judgments that are inexcusable, that are reprehensible." As a result, Kerry said, "time is ticking" and al-Assad is not likely to remain in power much longer.
At the end of his opening remarks, a protester interrupted the proceeding and shouted, "I'm tired over my friends in the Middle East dying," and Kerry addressed that after she was led out of the room.
"When I first came to Washington and testified, I obviously was testifying as part of a group of people who came here to have their voices heard. And that is, above all, what this place is about," he said.
He said the woman was "voicing her concerns about that part of the world. And, he said, knowing that his fellow senators have traveled there, "I know you heard this kind of thing.
"People measure what we do. And, in a way, that's a good exclamation point to my testimony. "
If approved by the committee, Kerry's nomination will go to the full Senate. Before he spoke, outgoing Secretary of State Hillary Clinton, U.S. Sen. John McCain, R-Arizona, and U.S. Sen. Elizabeth Warren, D-Massachusetts, praised Kerry and called for his confirmation.
President Barack Obama nominated Kerry last month.
"Over these many years, John's earned the respect and confidence of leaders around the world. He is not going to need a lot of on-the-job-training," Obama said.
"I think it is fair to say that few individuals know as many presidents and prime ministers or grasp our foreign policies as firmly as John Kerry, and this makes him a perfect choice to guide American diplomacy in the years ahead."
Asked about Afghanistan, Kerry said the first priority is to transition security responsibility to the Afghan forces and "maintain a capacity to prevent the kind of basing for terrorism which took us there in the first place."
"There will be a counterterrorism mission that will continue. President Obama's been very clear about the fact that that the counterterrorism mission will continue beyond 2014. And that the training will probably continue beyond 2014," he said. "So there is going to be, according to the president's own statement, some measure of engagement, but the effort is to have the Afghans in the lead. Continued training of the forces. Build an enduring partnership with Afghanistan. And support an Afghan-led reconciliation. Not a U.S.-led, but Afghan-led reconciliation if it is possible. "
Sen. Bob Corker, a Tennessee Republican, expressed concern about the secretary of defense nominee, former Republican Sen. Chuck Hagel -- disliked by some Republicans and conservatives because of his views.
Corker said Hagel's affiliation with a group called Global Zero is "just concerning." The group is devoted to eliminating nuclear weapons, and Corker doesn't want the U.S. nuclear arsenal to be weakened.
But Kerry said Hagel is "realistic." And the Global Zero initiative "is not talking about today's world."
"It's a goal. It's an aspiration. And we should always be aspirational," he said. "But it's not something that could happen in today's world, and nor could any leader today sit here or in any other chair and promote to you the notion that we ought to be cutting down our deterrent level below an adequate level to maintain deterrence."
He said Hagel is "a strong patriotic former senator, and he will be a strong secretary of defense."
Kerry touched on various other issues, including Latin America, Mali, Somalia, Russia, the plight of women and girls in Asia, and the foreign affairs budget being "less than 1% of the entire budget of government."