[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/10/28/art.nancycu1028.gi.jpg caption="Sharp differences among Democrats over abortion and immigration have raised questions over whether Speaker Nancy Pelosi currently has the 218-vote majority needed for passage of the bill."]Washington (CNN) - A hotly anticipated health care reform vote by the full House of Representatives may be delayed until Sunday, according to two Democratic sources.
But the vote on the nearly $1.1 trillion bill is still tentatively scheduled for Saturday, the sources noted.
The sources blamed the potential postponement on GOP delaying tactics. Sharp differences among Democrats over abortion and immigration, however, have raised questions over whether Speaker Nancy Pelosi currently has the 218-vote majority needed for passage.
Republican leaders added to the turmoil Friday morning, seizing on news of spiraling unemployment to warn that new taxes and regulations including in the sweeping reform measure would push the country into an economic abyss.
President Barack Obama, meanwhile, prepared for a rare Saturday Capitol Hill visit to twist Democratic arms on what has become a virtual make-or-break issue for his young administration.
Related: Health care wins two big backers
The question of abortion coverage in the health care bill has bedeviled top Democrats for weeks. Under its current language, the measure would allow individuals to purchase policies through a new insurance exchange that would cover abortion procedures. Anti-abortion rights Democrats, led by Michigan Rep. Bart Stupak, have argued that provisions designed to prevent tax dollars from being used to directly pay for such services are inadequate.
Stupak is one of up to 40 anti-abortion Democrats reportedly unsatisfied with the language - potentially enough to strip Pelosi of the 218-vote majority needed to pass the bill.
Democratic leaders may turn to compromise language drafted by Rep. Brad Ellsworth, an Indiana Democrat opposed to abortion rights. Ellsworth has proposed using private contractors to pay providers of abortion services - an idea that has come under fire from both supporters and opponents of abortion rights.
At the same time, members of the Congressional Hispanic Caucus staunchly oppose adding a provision to the bill that would bar undocumented workers from using their own money to buy health insurance policies available through the exchange.
The measure is already included in the Senate Finance Committee's version of the bill, and is backed by the White House. Some conservative House Democrats have also indicated their support for the Senate language.
Pelosi's bill currently includes various requirements for immigrants to verify their citizenship before getting federal subsidies to buy health insurance. Conservatives, however, have called the requirements insufficient.
–CNN's Dana Bash, Lisa Desjardins and Deirdre Walsh contributed to this report.