President Obama on Sunday hailed the fourth anniversary of the Affordable Care Act and said it was “now last call” for consumers to sign up for 2014 coverage.

“If you’re an American who wants to get covered – or if you know someone who should – it’s now last call for 2014,” said Obama in a statement.

The president touted the law’s benefits and said it had kept health costs down while boosting coverage.

“Since I signed the Affordable Care Act into law, the share of Americans with insurance is up, and the growth of health care costs is down, to its slowest rate in fifty years - two of the most promising developments for our middle class and our fiscal future in a long time,” said Obama.

“More Americans with insurance have gained new benefits and protections – the 100 million Americans who’ve gained the right to free preventive care like mammograms and contraception, the eight million seniors who’ve saved thousands of dollars on their prescription drugs, and the untold number of families who won’t be driven into bankruptcy by out-of-pocket costs, because this law prevents insurers from placing dollar limits on the care you can receive,” he added.

“More Americans without insurance have gained coverage. Over the past four years, over three million young Americans have been able to stay on their family plans,” said the president.

Obama also touted the 5 million consumers who have signed up since the launch of in October. The enrollment drive, though, will likely fall short of the administration's initial 7 million target and numbers show that the share of young, healthy consumers needed to keep costs down is only 25 percent, below the 40 percent initial goal.

The administration has also been forced to delay a number of key provisions of the law, but so far has refused to push back the March 31 deadline for open enrollment. After that date, consumers without insurance must pay a penalty. The administration, though, has suggested that those who have begun the process for obtaining coverage may be given additional time to finish their applications on that date.

Critics say that the problems with and the multiple delays are proof Obama's signature domestic achievement was never ready for prime time. Republican lawmakers are vowing to press ahead with efforts to block the law and question if Obamacare has actually increased the number of Americans with insurance.

Obama on Sunday said that individual Americans’ experiences with Obamacare “will ultimately determine the fate of this law.”

But he vowed to work to implement its provisions. The president cited a letter from a woman who signed up for coverage and told him that she “felt like a human being again.”

“This is what’s at stake any time anyone, out of some outdated obsession, pledges to repeal or undermine the Affordable Care Act,” said Obama. “And that’s why my administration will spend the fifth year of this law and beyond working to implement and improve on it.”