President Barack Obama hit back on Sunday at criticism by Republican presidential candidates of his handling of Iran and other international issues, and said a new Congress may be needed to heal the U.S. economy.

In his home state of Hawaii, the Democratic president appeared to relish the chance to defend and tout his foreign policy record at a news conference wrapping up a summit of Asia-Pacific leaders that he hosted.

Speaking in front of a setting sun over an ocean cove, Obama said his frank and open relationship with China had "yielded considerable benefits" including a united front against Iran's nuclear ambitions.

Asked to respond to Republican candidate Mitt Romney's assertion that Iran would succeed in developing a nuclear weapon if Obama were to be re-elected, the president cited "steady, determined, firm progress in isolating the Iranian regime."

Obama said sanctions he has pushed have had "enormous bite" on Iran's economy and influence, and he stressed that while he preferred a diplomatic resolution to the dispute, no option was off the table.

"Is this an easy issue? No. Anybody who claims it is either politicking or doesn't know what they're talking about," Obama said.

Romney is the current front-runner for the Republican presidential nomination to face Obama in the November 2012 election, when Obama is seeking a second term in office.

Obama was similarly direct in responding to questions about statements by some Republican candidates endorsing waterboarding, an interrogation technique that simulates drowning that Obama ended when he took office.

During a Saturday debate among the Republican presidential candidates in South Carolina, businessman Herman Cain and U.S. congresswoman Michele Bachmann backed the use of waterboarding.

"They're wrong. Waterboarding is torture," Obama said. "Anybody who has actually read about and understands the practice of waterboarding would say that that is torture. And that's not something we do -- period."

The United States used waterboarding on some foreign terrorism suspects under former President George W. Bush, a Republican. During the Republican debate, congressman Ron Paul and former U.S. ambassador to China Jon Huntsman opposed waterboarding as torture.

Economic concerns

Concerns about the U.S. economy have dominated the presidential campaign so far. But the eight Republican White House hopefuls switched during the Saturday debate to talk extensively about international affairs. None of the Republican candidates has much foreign policy experience except for Huntsman, who is trailing in the polls.

Obama has proven to be popular on the international stage, and foreign policy may be a strength, especially following the U.S. killing of al Qaeda leader Osama bin Laden in May and with the winding down of wars in Iraq and Afghanistan.

But the 2012 election is expected to hinge on Obama's economic record, with the U.S. unemployment rate at 9 percent in spite of his economic stimulus efforts and auto industry bailout.

At the post-APEC news conference, Obama said he was ready to "keep chipping away" at congressional opposition to his $447 billion jobs bill, which was rejected in Congress as a whole and is now being pursued piece by piece.

"I'll keep on pushing until we get all of it done. And that may take me all the way to November to get it all done. And it may take a new Congress to get it all done," he said, digging in his heels against Republicans who say the plan is too costly at a time of fiscal strain.

"Do I anticipate that at some point they recognize that doing nothing is not an option? That's my hope. And that should be their hope, too, because if they don't, I think we'll have a different set of leaders in Congress," Obama said.

(Additional reporting by Samson Reiny; Editing by Will Dunham)