U.S. President Barack Obama speaks during a news conference with David Cameron, U.K. prime minister, in the Rose Garden of the White House in Washington, D.C., U.S., on Wednesday, March 14, 2012. Photographer: Andrew Harrer/Bloomberg

President Obama said Tuesday the fact that more than 7.1 million Americans had signed up for health insurance over the past six months showed “the Affordable Care Act is here to stay.”

“But the bottom line is this:  Under this law, the share of Americans with insurance is up and the growth of health care costs is down, and that’s good for our middle class and that’s good for our fiscal future,” he said, standing in the Rose Garden with Vice President Biden. “And there’s no good reason to go back.”

Recounting the tales of three Americans who have been helped by the law — including a woman who was diagnosed with cancer after getting covered under the law -- Obama said that was the point of the law: ”Making sure that all of us, and all our fellow citizens can count on the security of health care when we get sick.”

He also said congressional Democrats should be proud of having helped enact the law, even as they come under attack this year.

“We could not have done it without them, and they should be proud of what they’ve done,” he said, warning that Republicans could pay a price for their opposition. “In the end, history is not kind to those who would deny Americans their basic economic security. … That’s what the Affordable Care Act represents.”

Obama mocked GOP attacks on the law. "There are still no death panels," he said. "Armageddon has not arrived."

“This law is doing what it’s supposed to do,” the president said. “It’s working, it’s helping people from coast to coast.”

Obama cautioned that there were still problems in the nation’s health care system.

“This doesn’t mean all the problems with health care have been solved,” he said. “But the debate over repealing this law is over.”