WASHINGTON — House Democrats acknowledged they don't yet have the votes to pass a sweeping overhaul of the nation's health care system, and signaled they may push back the vote until Sunday or early next week.

Majority Leader Steny Hoyer, D-Md., told reporters in a conference call Friday that the make-or-break vote on President Barack Obama's push to make health coverage part of the social safety net could face delay. Democrats were originally hoping to pass the bill on Saturday—and officially, that's still the plan.

But Democrats have yet to resolve a intraparty disputes over abortion funding and illegal immigrants' access to medical coverage. They cleared one hurdle Friday when liberals supporting a government-run Medicare-for-all system withdrew their demand for a floor vote.

Hoyer sought to pin the blame for any possible slippage on delaying tactics expected from Republicans, who unanimously oppose the health care remake.

"Nice try Rep. Hoyer, but you can't blame Republicans when the fact is you just don't have the votes," said Antonia Ferrier, spokeswoman for House Republican Leader John Boehner of Ohio. Republicans could stall the bill by demanding roll-call votes on parliamentary matters.

Hoyer acknowledged that Democrats are still short of the 218 votes they need to pass the bill. "There are many people who are still trying to get a comfort level that this is the right thing to do," he said. "We're very close."

While Hoyer said he still expects a vote Saturday evening, he said he has put lawmakers on notice they may be called to the House floor Sunday afternoon, or even Monday or Tuesday.

The White House issued a formal endorsement of the House bill Friday, and said Obama plans to go to Capitol Hill on Saturday to rally Democrats. House passage of the 10-year, $1.2 trillion legislation that extends health coverage to tens of millions of uninsured Americans and puts tough new restrictions on insurance companies would be a breakthrough for his agenda.

A moderate Democrat, South Dakota Rep. Stephanie Herseth Sandlin, announced Friday she would not vote for the House bill — but held out the possibility she could support final passage of the legislation, after compromises with the Senate. Sandlin said she fears the House bill could diminish access to health care in her state.

Action on health legislation was slowed as senators waited for the Congressional Budget Office to weigh in on a bill written by Majority Leader Harry Reid in consultation with the White House and key committee chairmen. Senate votes could slip until next year, but in the House Democratic leaders pressed forward.