President Obama on Friday dismissed criticisms that the botched rollout of Obamacare and other mishaps produced a lost year for the White House, brushing aside increasingly negative views of his presidency while insisting his administration could tackle big issues in his second term.

In a sign of just how brutal 2013 has been for Obama politically, the president in his last news conference of the year was forced to assess whether the past 12 months was his worst stretch since taking office.

"That's not how I think about it," Obama insisted, choosing to focus on a recent surge in Obamacare enrollments and a policy wish list stalled by gridlock on Capitol Hill.

"If you're measuring this by polls, my polls have gone up and down a lot," Obama added.

However, a series of recent polls show Obama with his lowest approval ratings ever, hovering around 40 percent.

The main cause of that downward trend was the problem-ridden rollout of Obamacare, which took a toll on how Americans view the president personally and hardened negative attitudes about whether Washington can tackle the nation's most pressing issues.

"Since I'm in charge, obviously we screwed it up," the president said of Obamacare, when asked to assess his biggest failure of 2013.

The president announced that more than 500,000 people had signed up for Obamacare on in the first three weeks of December — a higher figure than the months of October and November combined.

The Obama administration, in a surprise move late Thursday, said that millions of Americans facing insurance cancellations next year won't have to pay a fine if they don't obtain health care coverage.

Obama bristled, though, when asked whether yet another delay would weaken public confidence in the health law.

"The majority of them are either keeping their old plan ... or they're finding a better deal in the marketplace," Obama said of those on the receiving end of cancellation notices.

The major policy shift, outlined in a letter from Health and Human Services Secretary Kathleen Sebelius to Democratic lawmakers, is the latest attempt by the White House to atone for Obama's broken promise that all Americans could keep their insurance plans under Obamacare.

The delay, which comes on the heels of pushing back enforcement of other core provisions of the Affordable Care Act, also gives Republicans ammunition to argue that the president's signature domestic achievement was not ready for prime time.

The president has also delayed the employer mandate, the cap on out-of-pocket medical expenses and requirements for small businesses, among other measures.

The latest change came just before a Monday deadline for consumers seeking Obamacare coverage on Jan. 1.

It also undermines a common White House talking point in recent months: that the individual mandate, the centerpiece of the Affordable Care Act, would be enforced as planned.

"The individual mandate timing has not changed," White House press secretary Jay Carney said in late October. "The deadline for signing up for insurance was and is March 31st."

The White House had previously said that insurers could extend canceled policies through 2014, but many of the largest insurance providers declined to comply with the request.

Republicans of late have pointed out that just 365,000 people signed up for Obamacare in October and November, amounting to only a fraction of those whose plans were canceled. The White House has struggled to combat criticisms that more people would lose coverage than gain it at the start of 2014.

Those with cancellation notices can receive hardship exemptions for catastrophic coverage, an insurance plan that was made available to a small fraction of younger Americans through Obamacare.

And insurance companies blasted the announcement from the White House, saying it could disrupt the marketplaces and undermine preparations for the most sweeping change to the health care system since Medicare.

Although the president suggested his administration had mostly fixed the federal Obamacare website, his critics pointed to what they consider a piece of delicious irony: wasn't working as Obama addressed the White House press corps.