In his final White House news conference of the year, the president declined to say whether 2013 -- the fifth year of his presidency -- was the worst, given the flawed rollout of the Affordable Care Act, controversy over domestic surveillance practices and erosion of his approval ratings.
He began the news conference by citing upbeat reports on economic growth, employment and expansion of the number of Americans getting healthcare coverage.
"We head into next year with an economy that is stronger than it was at the start of the year," Obama said. "I firmly believe that 2014 can be a breakthrough year for America."
Asked whether 2013 was his worst year as president, he said his poll numbers "have gone up and down a lot through the course of my career."
"If I was interested in polling, I wouldn't have run for president," he said.
Asked what he thought his biggest mistake of the year was, Obama said it was the flawed rollout of the Affordable Care Act -- commonly known as Obamacare.
"When it came to the healthcare rollout, even though I was meeting every other week or every three weeks emphasizing that consumers have a good experience ... the fact is that it didn't happen in the first month, six weeks, as it should have, was not good," the president said.
"I'm in charge. We screwed it up," he said.
Obama called on Congress to take further action in 2014 to promote jobs and economic growth, and to extend unemployment insurance for long-term jobless workers.
The president credited House Budget Committee Chairman Paul Ryan, R-Wis., and Senate Budget Committee Chairwoman Patty Murray, D-Wash., for doing "a good job in trying to narrow the difference and pass a budget I can sign," but said congressional Republicans had engaged in too much "brinksmanship" on critical issues.
He said he will not negotiate with Congress over raising the federal borrowing limit when it comes up in February.
"No, we're not going to negotiate with Congress to pay bills that it has accrued," Obama said.
The president said he will recommend changes early next year in national security domestic surveillance practices. He said data should be collected and processed in a way that gives the public "more confidence" that privacy is protected, but insisted "we can't unilaterally disarm."
"The values that we've got as Americans are ones that we have to be willing to apply beyond our borders more systematically than we have in the past," he said.
Obama said a tentative agreement with Iran on its nuclear program could lead to "a resolution to a problem that has been a challenge for U.S. national security for more than a decade now and that is getting Iran to, in a verifiable fashion not pursue a nuclear weapon."
"The alternative is possibly us having to engage in some sort of conflict the resolve the problem," he said.
"I'm keeping all options on the table," the president said, but repeated he would prefer to resolve the issue through diplomacy.
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