WASHINGTON - Americans are getting their first look on Saturday at whether a five-week, round-the-clock technology overhaul has made it easier to use the troubled website that is the backbone of President Barack Obama's landmark healthcare overhaul.

The White House had pledged that HealthCare.gov, which has been plagued by errors, outages, and slow speeds since its disastrous October 1 launch - would be working for most people this weekend.

Fixing the crisis, one of the biggest of Obama's presidency, has enormous political stakes for the administration and its Democratic allies who are heading into congressional elections next year.

The administration said on Saturday that 90 percent of website users can now create an account on the system, which is meant to help millions of people sign up for new health insurance plans.

But officials did not immediately provide information on whether a flurry of recent hardware and software upgrades has fixed other parts of the system to the point where a similar percentage of users could complete their enrollment.

Officials have been careful to say that the overhauled site won't work for everyone and could still be overwhelmed by traffic at times.

"There will be moments, most likely in the middle of the day, where demand will be greater than that capacity," Jeffrey Zients, the Obama confidante tasked with leading the rescue mission, told reporters earlier this week.

His tech team created a new "queuing" feature that, in peak periods, will suggest a better time to return to the site. The administration has also directed users to visit it during off-peak hours in the morning, evening and weekend.

The HealthCare.gov website is the main way for people in 36 states to sign up for healthcare coverage under the 2010 Patient Protection and Affordable Care Act, also known as Obamacare.

The Obama administration hopes eventually to enroll about 7 million uninsured and under-insured Americans in 2014, with many of those consumers expected to qualify for subsidies.

The healthcare overhaul is Obama's signature domestic achievement, a program designed to extend coverage and reduce healthcare costs. Opponents, including many Republicans, view it as a massive government intervention into private medicine that will inflate healthcare costs.

To work, the program must enroll millions of young, healthy consumers whose participation in the new insurance exchanges is key to keeping costs in check.

SUCCESS TOUGH TO MEASURE

On Friday evening, ahead of the Obama administration's self-imposed Saturday deadline to get the insurance shopping website working for the "vast majority," the Centers for Medicare and Medicaid Services (CMS) announced it was taking down the website for an unusually long 11-hour maintenance period.

The website's account creation and log-in functions appeared to work smoothly by 8 a.m. (1300 GMT) on Saturday, avoiding the crash and error messages seen at its launch. But technology specialists told Reuters that it would be difficult to independently assess whether the site has met the goal of functioning for most users most of the time, including handling 50,000 users at once.

"There won't be anything you can tell from the outside," said Jonathan Wu, an information technology expert and co-founder of the consumer financial website ValuePenguin.

Wu said HealthCare.gov is working better but any remaining problems lie much deeper within the site.

Questions remain about the site's ability to direct payments to private insurance companies when consumers enroll in their plans. Portions of the system handling those functions are still being built, officials say.

"The real tests are: Were my premium payment and subsidy accurately calculated? Am I getting the coverage I signed up for? If my income situation changes, will the reconciliation occur in a timely fashion?" said Rick Howard, a research director at technology consultant Gartner.

Zients was set to brief reporters on the site's progress on Sunday. If the website does not work for the "vast majority" of visitors this weekend as the administration has promised, uninsured Americans could face problems getting coverage by an initial December 23 deadline.

It also could create ripples that extend to the 2014 elections when control of the U.S. House of Representatives, now dominated by Republicans, and the Senate, where Democrats have a majority, will be up for grabs.

Congressional Democrats facing re-election already have shown signs of distancing themselves from the president and his healthcare program. If the website does not show significant improvement soon, some Democrats - particularly the dozen U.S. senators from states led by conservative Republicans and who are up for re-election next year - might call for extending Obamacare's final March 31 enrollment deadline for 2014.

That would delay the fines that are mandated by the law for those who do not have insurance by that date, a scenario that insurers say would destabilize the market. It also would fuel Republicans' arguments that Obamacare is fatally flawed and should be scrapped.

HealthCare.gov's immediate success has also become vital to Obama's credibility, which polls indicate has been tarnished by the site's problems as well as his admission that he overreached in promising that everyone who liked their healthcare plan would be able to keep it under the new law.

"It is a lot harder to reboot public trust than it is to reboot software," said David Brailer, chief executive of the Health Evolution Partners private equity firm and a health official in former President George W. Bush's administration.