BOSTON (CNN) - President Barack Obama acknowledged Wednesday the national health care law's new website was "too slow" and too many people "have gotten stuck" in it.
"I'm not happy about it and neither are a lot of Americans who need health care," he said at a Boston rally to tout and defend the Affordable Care Act, which is the signature domestic achievement of his presidency.
"There is no excuse for it and I take full responsibility for making sure it gets fixed ASAP. We are working overtime to improve it every day," Obama said.
The President delivered his address at Boston's Faneuil Hall, the Colonial-era meeting house where then-Massachusetts Gov. Mitt Romney signed into law a sweeping health plan.
The President says that Obamacare was modeled on the Massachusetts law.
"This is the hall where seven years ago Democrats and Republicans came together to make health reform a reality for the people of Massachusetts. It's where then Gov. Mitt Romney, Democratic legislators, Sen. Ted Kennedy, many of the folks here today joined forces to connect the progressive vision of health care for all with some ideas about markets and competition that had long been shared by conservatives," said Obama.
The President compared the current extremely rough start up for the health care exchanges in the national law to what happened in the Bay State, saying that health care reform in Massachusetts was a success despite "early problems" and "changes that had to be made."
He added that negative predictions from government coverage "didn't come true."
And Obama challenged Republican opponents of Obamacare to come up with helpful ideas for health care instead of undermining the federal law.
"Anyone defending the old broken system" or lacking any plan to help uninsured or underinsured Americans get coverage "should have to explain themselves," he said.
Hours before Obama's event, Romney criticized the national health care law.
In a statement, Romney revived a line he used quite often on the campaign trail in opposing Obama in last year's presidential election.
"In the years since the Massachusetts health care law went into effect, nothing has changed my view that a plan crafted to fit the unique circumstances of a single state should not be grafted onto the entire country," Romney said.
"Beyond that, had President Obama actually learned the lessons of Massachusetts health care, millions of Americans would not lose the insurance they were promised they could keep, millions more would not see their premiums skyrocket, and the installation of the program would not have been a frustrating embarrassment," Romney said.
"Health reform is best crafted by states with bipartisan support and input from its employers, as we did, without raising taxes, and by carefully phasing it in to avoid the type of disruptions we are seeing nationally," he said.
Romney was not at the President's address.
David Simas, a senior White House strategy and communications official, told reporters this week that regarding the President's Wednesday speech, "No, there's no outreach to Governor Romney."
A source close to the former governor told CNN that Romney was not invited to the event.
Prior to the address, a former Romney campaign adviser and spokesman had low expectations for the President's speech.
"Unless he stands up in Faneuil Hall and unveils a revamped, working website and admits he misled the country about how their insurance policies would be affected, it will be just another Obama speech. One full of empty promises, self-serving rhetoric and intellectual dishonesty," said Kevin Madden, a Republican strategist and CNN contributor.
Stuart Stevens, a former top adviser to Romney's 2012 campaign, compared news coverage of Obamacare to news coverage of the Vietnam War in the 1960's and 1970's, which started out non-controversial before becoming extremely critical of U.S. efforts.
"This coverage is so much like the coverage of Vietnam. It was all great for so long until reporters really got on the ground and saw the reality," Stevens told CNN.
- CNN's Kevin Liptak contributed to this story.