Healthcare.gov, the federal Obamacare exchange, is expected to be taken offline for as many as 12 hours during all but one Sunday over the open enrollment period.

The Department of Health and Human Services is planning website outages from midnight to noon every Sunday except Dec. 10, according to slides from a navigator that journalists posted on Twitter. The agency is also planning to take the exchange offline overnight during the first day of open enrollment, on Nov. 1.

The slides encouraged navigators to "please mark your calendars with these times and plan accordingly."

More than three dozen states use healthcare.gov for their marketplaces, which allow people who don't receive insurance through a job or through a government program to buy private, tax-subsidized coverage. Navigators help people enroll in coverage and answer questions about Obamacare for potential customers.

According to the Centers for Medicare and Medicaid Services, the outages will last no more than 12 hours but the actual outage times could be shorter.

When asked about the slides, a CMS representative said that "maintenance outages are regularly scheduled on healthcare.gov every year during open enrollment."

"This year is no different," the spokesman said. "The maintenance schedule was provided in advance this year in order to accommodate requests from certified application assisters. System downtime is planned for the lowest-traffic time periods on healthcare.gov including Sunday evenings and overnight."

The Trump administration has been accused by Democratic lawmakers of attempting to "sabotage" Obamacare and undermine its success by seeking ways to reduce enrollment. It has cut the open enrollment period in half, to six weeks, which would end the period Dec. 15, and slashed funding on navigators and ads.

The administration has countered that the shortened timeline was intended to bring the enrollment period in line with that of Medicare and has said that navigators were paid $62.5 million in federal grants to sign up just 81,426 people, which is about 0.7 percent of total enrollees. Roughly 9 million people enrolled in the federal exchange by the end of last year's open enrollment.

During the first open enrollment, in 2013, healthcare.gov faced technical problems including long wait times, which prevented people from enrolling in coverage and led to deadline extensions. The issues led to the resignation of former HHS Secretary Kathleen Sebelius. In later years the same problems did not occur as the site underwent various makeovers.

On the first day of the second open enrollment, roughly 34,000 accounts were created and about 60,000 people submitted an application for coverage, according to a report from the HHS Office of the Inspector General. The site had more than 650,000 unique visitors.

A former HHS official who helped oversee previous open enrollments told the Washington Examiner that such scheduled website outages for maintenance were not the norm when former President Barack Obama was in office.

"This is not normal," the former official said. "No excuse. They're blocking people's access to healthcare and sabotaging the law because it's named Obamacare."