* Contractors shift blame for Healthcare.gov problems
* White House: signup can take place right up to March 31
* Denies signup adjustment a response to website woes
* Some Democrat comments could fuel Republican delay efforts
WASHINGTON, Oct 23 (Reuters) - The contractors for the government's troubled healthcare website sought to deflect blame on Wednesday as more Democrats voiced concerns about the implementation of President Barack Obama's signature domestic policy.
Administration officials, in damage-control mode for nearly a week, held a closed-door briefing for Democrats in the U.S. House of Representatives and a private session with insurance company executives, who said they would assist in efforts to fix the Healthcare.gov website.
Websites are the primary vehicle for consumers to shop for insurance through exchanges set up under the healthcare program.
With the rocky launch of the "Obamacare" insurance exchanges entering its fourth week, additional Democrats came forward, some urging the president to extend the open-enrollment period for buying health insurance through the program beyond the existing March 31 deadline.
One Democrat, Senator Joe Manchin of West Virginia, said he would join a Republican effort to delay the so-called "individual mandate," that requires people to buy insurance or face a tax penalty.
Manchin, in a Fox News interview on the "The O'Reilly Factor," called for a transition year with no fines. "Let's work through the problems. We've got a lot of problems, they have been identified. I think everybody has recognized them. Let's fix it. Let's get together and fix things," he said.
White House officials said on Wednesday that enrollment requirements were being changed so that consumers could sign up for health insurance right up to the March 31 deadline and avoid penalties. Some people previously needed to be signed around Feb. 15 to meet the end of March deadline.
A White House official said that pushing back the sign-up requirement was not related to glitches with Healthcare.gov, but was simply an effort to eliminate confusion over the two deadlines.
The comments from the handful of Democrats posed a new potential hazard for the White House and gave Republicans a chance to portray their efforts to derail the healthcare program as bipartisan.
Democratic Senator Mark Pryor of Arkansas, who faces a tough re-election race next year, said he agreed with fellow Democrat Jeanne Shaheen of New Hampshire that the open enrollment period to sign up for insurance should be extended beyond March 31, 2014.
Representative James Clyburn of South Carolina, the third-ranking House Democrat, criticized the website for forcing consumers to provide private information before deciding what kind of health insurance plan they want to buy.
"I've talked to too many people who tell me before they ever get around to figuring out what it is they want to buy, they're having to answer questions that they don't feel they should be answering," Clyburn said.
Republicans said they would intensify their investigations into the launch of the 2010 Affordable Care Act, known as "Obamacare."
"It is our job to hold them accountable, and when it comes to Obamacare clearly there is a lot to hold accountable," House of Representatives Speaker John Boehner told reporters.
The Republican-led House Energy and Commerce Committee on Thursday will hear from the top contractors responsible for the program. They included website developer CGI Federal, a unit of Canada's CGI Group Inc, which said in prepared testimony that the software from another contractor designed to allow users to create an account led to early bottlenecks.
But the other contractor, United Health Group unit Quality Software Services Inc (QSSI), said in prepared testimony that some of its problems stemmed from a late decision by the administration to require consumers to register for an account before browsing for insurance products.
"This may have driven higher simultaneous usage of the registration system that wouldn't have occurred if consumers could 'window shop' anonymously," said QSSI.
The company's software is now keeping pace with demand. Andrew Slavitt, executive vice president with QSSI's parent, said the software has had "error rates close to zero" since Oct. 8.
Obama administration officials, including U.S. Health and Human Services Secretary Kathleen Sebelius, met with the chief executives of 14 leading insurance companies, including Aetna Inc, WellPoint Inc and Humana Inc.
The executives agreed to form new technical teams with the administration to help fix the website, which provide online access to the marketplaces designed to be the main way for millions of uninsured Americans to research and buy health insurance plans under the law.
"We had a candid discussion on the challenges facing the exchange, and the plan that is being put in place to get the program on track," Aetna Inc spokeswoman Cynthia Michener said.
The Oct. 1 debut of the exchanges was marred by technical glitches that have kept many from signing on and making purchases. Those unable to sign up online can call a toll-free telephone number as an alternative.
The administration has so far declined to disclose the number of enrollments, either online or by telephone.
'WORKING HARD TO FIX THE PROBLEMS'
A prolonged delay in getting Healthcare.gov to work could jeopardize White House efforts to sign up as many as 7 million people in 2014, the first full year the law takes effect. The administration this week began what it called a "tech surge," bringing in experts led by the administration's top economic aide Jeffrey Zients to analyze and fix the problems.
"I think what we learned is they're working hard to fix the problems," Representative Sander Levin of Michigan, senior Democrat on the House Ways and Means Committee, said after Wednesday's briefing.
The U.S. Health and Human Services Department will begin regular news briefings on Thursday to provide updates on "the progress that's being made and on the efforts that are being undertaken, both to address the technical problems and to make the whole experience for American consumers better," White House spokesman Jay Carney said.
House Democrats said there was no discussion in the briefing about whether the problems should lead to a delay of the individual requirement that every American have insurance or pay a tax penalty. The Congressional Budget Office has estimated a delay would reduce enrollment significantly.
REPUBLICANS DEMAND DELAY
Republicans, who have fought the healthcare law as an unwarranted extension of the federal government, said the requirement should be delayed until the problems with the rollout are resolved.
"With so many unanswered questions and the problems arising around this rollout, it doesn't make any sense to impose this one percent mandate tax on the American people," House Majority Leader Eric Cantor told reporters on Wednesday.
Republicans have repeatedly tried to derail or delay the healthcare law since taking control of the House in the 2010 elections. They demanded more answers on Wednesday about the scope of the problems.
Three committees in the Republican-controlled House have announced investigations of the law's rollout, which Cantor described as "nothing short of a debacle."