U.S. Sen. John Kerry testified today to his colleagues on the Senate Foreign Relations Committee, at a confirmation hearing on his nomination to be U.S. Secretary of State.

A lone protester shouting about the Middle East interrupted the hearing. Just as Kerry completed his prepared testimony, the woman began shouting about the Middle East. She was escorted from the room.

Kerry alluded to the interruption, telling the Foreign Relations Committee he respects the tradition of free speech and thought.

On Iran, Kerry said it's up to Iran to prove that its nuclear program is for peaceful purposes.

He said President Barack Obama has made it clear that "we will do what we must to prevent Iran from obtaining a nuclear weapon." Kerry added that "the clock is ticking on our efforts to secure responsible compliance."

Kerry says he's still hopeful that the U.S. and other nations can make progress on the diplomatic front.

On another issue, Kerry was asked about his past outreach to Syria's Bashar Assad -- but he said that's all irrelevant now because of Assad's unending violence against his citizens amid a two-year civil war. He said he doesn't think Assad has much time left as Syria's leader.

Republican Sen. John McCain -- a critic of Obama's policy on Syria -- told Kerry that the U.S. needs to do more to help rebels there, even if it doesn't send ground troops.

Kerry said the U.S. needs to continue discussions with Russia and others about Syria -- but he said he's not optimistic.

Kerry also said he supports deeper ties with China and is unconvinced the U.S. needs to ramp up its military presence in the Asia-Pacific region.

The Obama administration has made a stronger presence in Asia a foreign policy priority.

That's been welcomed by nations in the region unnerved by China's growing power and assertiveness, but has irked Beijing.

Kerry said the U.S. already has a lot more bases in the region than any other nation, including China, and augmenting them further could prompt Chinese concern of encirclement.

Kerry added that vigilance was still required and he was not suggesting retreating from "current levels."

Kerry also found himself defending defense secretary nominee Chuck Hagel.

Republican Sen. Bob Corker questioned Kerry about Hagel's support for an 80 percent reduction of U.S. nuclear weapons. It's a major issue for the Tennessee lawmaker, who has the Y-12 nuclear facility in his state.

Corker raised serious concerns about Hagel, a former Republican senator from Nebraska.

Kerry defended Hagel as a strong patriot and insisted he would be a strong defense secretary. He said those nuclear reductions would be a goal for the world, but unrealistic in today's world.