WASHINGTON - The Obama administration says it will meet its self-imposed deadline of fixing the troubled health care website so that 50,000 people can log in at the same time starting late Saturday. Yet questions remain about the stability of the site, the volume of traffic it can handle and the quality of the data it is delivering to insurers.

Round-the-clock repair work since HealthCare.gov went live on Oct. 1 has produced fewer errors, and pages are loading faster.

But the site still won't be able to do everything the administration wanted, and companion sites for small businesses and Spanish speakers have been delayed.

Still, the White House hopes a website that is at least operating more smoothly after weeks of bad publicity about its troubles will mark a fresh start for Obama and the signature domestic initiative of his presidency, as well as give him a chance to salvage a second term that has been weighed down by health care law's rough start and other issues.

Administration officials said HealthCare.gov was "performing well" Saturday, the deadline set to have it working smoothly for the "vast majority of users," after overnight hardware upgrades to boost server capacity. The deadline fell during a long holiday weekend when traffic to the site likely would have been slower anyway and at a level unlikely to expose new technical issues.

More hardware upgrades and software fixes were planned for overnight Saturday to further improve speed and reduce errors.

"With upgrades last night and those planned for tonight, the team is continuing its ongoing work to make HealthCare.gov work smoothly for the vast majority of users," Julie Bataille, communications director for the Centers for Medicare and Medicaid Services, said Saturday in a blog post. CMS oversees the health care website and is a division of the Department of Health and Human Services.

Additional data on the website's progress was to be released today by Jeff Zients, the website's chief troubleshooter.

Obama promised a few weeks ago that HealthCare.gov "will work much better on Nov. 30, Dec. 1 than it worked certainly on Oct. 1." But, in trying to lower expectations, he said he could not guarantee that "100 percent of the people 100 percent of the time going on this website will have a perfectly seamless, smooth experience."

The nation's largest health insurer trade group said significant problems remain.

Karen Ignagni, president and CEO of America's Health Insurance Plans, said insurers have complained that enrollment data sent to them from the website include too much incorrect, duplicative, garbled or missing information. She said the problems must be cleared up to guarantee consumers the coverage they signed up for effective Jan. 1.

"Until the enrollment process is working from end to end, many consumers will not be able to enroll in coverage," Ignani said.

The first big test of the repaired website probably won't come for another couple of weeks, when an enrollment surge is expected as consumers rush to meet a Dec. 23 deadline so their coverage can kick in on the first of the year.

Avoiding a break in coverage is particularly important for millions of people whose current individual policies were canceled because they don't meet the standards of the health care law, as well as for a group of about 100,000 in an expiring federal program for high-risk patients.

The law requires most people who don't have health insurance to buy coverage or pay fines.

If HealthCare.gov seizes up again at crunch time, the White House may have to yield to congressional demands for extensions or delays in key requirements of the law, such as the individual requirement to get covered. Delaying the individual mandate, in turn, could lead to higher future premiums, since healthy people would no longer have an incentive to sign up.

For the system to be successful, the administration needs large numbers of mostly younger, healthy people to buy coverage to help offset the cost of insuring older people who generally use more health care services. Federal subsidies are available to those who qualify to help lower the cost of insurance.