A deeply frustrated President Barack Obama moved to quell a growing revolt in his party Thursday morning, announcing an administrative fix that would let health insurance companies extend existing policies for a year.

The announcement by Obama — at the top of what became an unscheduled, nearly hourlong press conference — came as Democrats in both chambers are eyeing legislative fixes that would go much further and require insurers to extend such coverage.

At times introspective and contrite, but also defiant and determined, Obama acknowledged that he needs to “win back some credibility” after “we fumbled the rollout” of the 2010 health care law.

Obama also admitted that he was not “informed directly that the website would not be working,” but he avoided blaming any specific person on his staff or in his Cabinet for that oversight.

“That’s on me, and that’s why I’m trying to fix it,” he said of problems with the rollout of the website and other parts of the law.

“There’s going to be a lot of evaluation of how we got to this point,” Obama said, noting he’s been asking a lot of questions.

He also said that his promise that people could keep insurance plans they liked was made in error.

“There is no doubt that the way I put that forward unequivocally ended up not being accurate,” the president said. He said he believed it was true at the time he said it because he thought 98 percent would be happy with their new options and the law’s grandfathering provision would take care of the other 2 percent.

Administration officials emphasized in a background call with reporters that the fix for canceled policies would not allow insurance companies to sell old policies to new customers, unlike a bill by House Energy and Commerce Chairman Fred Upton of Michigan to be voted on by the House on Friday.

The administrative fix, however, is far from a guarantee that people will be able to keep their plans if they like them.

Insurers would have to go along with it, as would state insurance commissioners.

It might be more accurate to describe Obama’s fix, as well as the Upton bill, as “If your insurer likes your plan, you can keep it for a year.”

The fix also does not prevent insurers from increasing the premiums on those plans.

A proposal by Sen. Mary L. Landrieu, D-La., would require that the plans be extended.

White House officials are slated to brief House and Senate Democrats in meetings Thursday, and it’s not clear yet if the fix will calm a party shaken by the rocky HealthCare.gov rollout and millions getting cancellation notices despite Obama’s promise.

House Minority Leader Nancy Pelosi, D-Calif., is backing a legislative fix as an alternative to the Upton bill.

Obama indicated that he is opposed to the Upton bill, but said he is open to legislative remedies as long as they do not undermine the overall law. He appeared contrite and acknowledged that the rocky rollout has hurt chances for Democrats next year, but said the glitches are his fault, not theirs.

He also could not guarantee that the HealthCare.gov website would be 100 percent fixed by the end of the month — and said he would not have compared it with shopping on Amazon or Travelocity if he knew it wasn’t going to work.

More broadly, he dismissed criticism from some of his fellow Democrats that he and his administration are too insular — noting he talks to lots of people every day. But he acknowledged that the botched rollout would require him to rebuild his credibility to push the rest of his agenda. That agenda — notably immigration and budget priorities — is floundering.

Speaker John A. Boehner dismissed the president’s proposal.

“I’m highly skeptical that they can do this administratively,” the Ohio Republican told reporters Thursday morning. He also said that overall Obamacare is “just not fixable.”

Matt Fuller contributed to this report.