"This is one I regret and I've said I regretted," Obama said.
The President also acknowledged the law's rough start.
"I think we all anticipated that there would be glitches," he said. "I don't think I anticipated or anybody anticipated the degree of the problems with the website."
When O'Reilly asked Obama why he did not fire Health and Human Services Director Kathleen Sebelius, Obama said he held everyone accountable.
"I promise you that we hold everyone up and down the line accountable," he said.