However, Obama also stressed that the team is now doing everything possible to get the website working "better, faster, sooner".
"And we are confident that we will get all the problems fixed," he pledged.
Obama also tried to make the case for his signature health-care overhaul. Despite the recent technical glitches, he argued, the Affordable Care Act was "much more" than just a website.
He suggested people "bypass the website and apply by phone or in person," while waiting for the website to be fixed.
Obama encouraged those uninsured Americans not to lose faith in the new online marketplace which has been launched just three weeks.
He put up several examples of Americans saving money on insurance plan offered on the online marketplace, and argued that the essence of the law is to make health insurance available to people.
"So here's the bottom line, the product, the health insurance is good. The prices are good. It is a good deal. People don't just want it, they're showing up to buy it," said Obama.
He said 20 million visitors have checked the website, which showed "the demand is there".
