"California needs to stay the course and transition people into the more comprehensive policies that meet the requirements of the Affordable Care Act," said Patrick Johnston, president of the California Assn. of Health Plans. "Consumers could see rate increases for extended policies that won't have the added value of ACA required benefits. And the exchange would be unbalanced with a pool of older, sicker people, causing additional increases in rates."

The administration had hoped the online marketplaces that opened Oct. 1 would give consumers attractive alternatives to their current coverage. But the flawed healthcare.gov website has prevented millions of potential shoppers from even seeing what kind of plan they could get next year.

"We fumbled the rollout of this healthcare law," Obama said, identifying the website and the cancellations as "two fumbles."

PHOTOS: The battle over Obamacare

"That's on me," he said, regarding the cancellation letters that millions of consumers have received. "That's something I deeply regret, because it's scary getting a cancellation notice."

He also took pains to assume responsibility for the problems, saying the public should blame him, not members of Congress who have repeated his statements that Americans could keep health plans they liked.

"They were making representations based on what I told them and what this White House and our administrative staff told them, and so it's not on them, it's on us," he said. "But it is something that we intend to fix."

Those words were designed, in part, to quell a revolt among Democrats on Capitol Hill who threatened to buck the White House and back legislation that would extend even more current health plans into next year and beyond.

House Republicans planned to vote on one such plan Friday.

White House aides dispatched to Capitol Hill to sell the president's alternative Thursday received a warmer reception than they did earlier in the week, Democratic lawmakers said. Some emerged from the meeting saying the plan had addressed their concerns, although some skeptics remained undecided about the GOP bill.

"I'm keeping open on it," said Rep. Nick J. Rahall II, a West Virginia Democrat who is expecting a tough reelection fight. Rahall said he had questions about how the fix would work and whether it would reassure his anxious constituents. "How will they have a peace of mind that these letters were wrong, that they can keep what they have? Will they get a follow-up letter? Will they be given options?"

Comments from House Speaker John A. Boehner (R-Ohio) that Republicans were not interested in fixing the law also appeared to dissuade Democrats from backing the GOP bill.

"The only way to fully protect the American people is to scrap this law once and for all," Boehner said in a news conference at the Capitol. "There is no way to fix this."

Several Democrats still want to vote on the issue as a way to telegraph to their constituents that they are listening to their concerns and standing up to the president.

Sen. Mary Landrieu (D-La.), who drafted a bill that was gaining support among Democrats, said after the president's announcement that she was "encouraged" but would continue to push her bill.

"We will probably need to make a legislative fix," she said.

noam.levey@latimes.com

kathleen.hennessey@latimes.com

michael.memoli@latimes.com

Peter Frost in Chicago, Lisa Mascaro and Christi Parsons in the Washington bureau, and Chad Terhune in Los Angeles contributed to this report.