WASHINGTON, Dec. 20 -- At the end of his fifth year in the White House, U.S. President Barack Obama on Friday rejected the year of 2013 as the worst of his tenure, and expected 2014 to be "a breakthrough year for America."

Speaking at his year-end news conference in the White House briefing room, Obama opened his remarks with the good news of the U.S. economic growth and cited the latest improvement of the health plans sign-ups under his signature healthcare overhaul.

Asked if 2013 had been the worst of his presidency, he laughed and dodged the question. He downplayed the recent poll results, as his approval rating has slid to all-time low of his presidency.

The latest CNN/ORC poll released about an hour before the president's year-end news conference showed his approval rating fell to 41 percent, the lowest of his presidency.

"If you are measuring this by polls, my polls have gone up and down a lot through the course of my career," said Obama. "If I was interested in polling, I would not have run for president."

"I've run my last political race. So at this point, my goal every single day is just to make sure that I can look back and say we're delivering something, not everything, because this is a long haul," he added.

The president admit that the problem with the health care website, which has been through a rocky rollout since Oct.1, was " a source of great frustration."

"The fact is it didn't happen in the first month, first six weeks, in a way that was at all acceptable. And since I'm in charge, obviously we screwed it up," said Obama.

But he moved quickly to stress that the enrollment number of the healthcare website has picked up pace in the past month, which he described as "a big deal."

"More than half a million Americans enrolled on HealthCare.Gov in the first three weeks of December alone," he said.

The figure outpaces the enrollment number for October plus November, and brings the total number under ObamaCare to more than 1 million.

The White House is trying to recover from months of negative news about the implementation of the healthcare overhaul, which is believed to have dragged down his approval ratings.

Several of the president's domestic legislative priorities, including tightening up gun control, made little progress at Capitol Hill in 2013. Obama vowed to gain ground in the upcoming new year.

"We head into next year with an economy that's stronger than it was at the start of the year," Obama said, "I firmly believe that 2014 can be a breakthrough year for America."

He regarded 2014 to be a "year of action" on moving forward the immigration reform, creating more jobs, and extending wages and benefits.

The latter half year of 2013 has also been dominated by breaking news of the leaks by former U.S. defense contractor Edward Snowden about the National Security Agency's top secret surveillance programs.

Obama defended the NSA's domestic phone records programs while promising some reforms in the upcoming new year. He said he would review the reform recommendations by a presidential advisory panel during his holiday break starting Friday, and would make a "pretty definitive statement" in January about some reforms.