WASHINGTON — House Democrats put the finishing touches on their health care legislation Friday and were close to adopting compromise language on the politically treacherous issue of insurance coverage for abortions, as party leaders and the White House pushed to lock in votes on the eve of a historic floor debate.

Democratic leaders said they were confident that they would have the 218 votes needed to pass the bill, but they continued to scramble behind the scenes. A planned visit to the Capitol by President Barack Obama was postponed until today so that a face-to-face appeal would have greater impact on wavering lawmakers just before the vote.

Vice President Joe Biden, Cabinet secretaries and other senior officials, including the White House chief of staff, Rahm Emanuel, worked the phones, imploring undecided Democrats to vote yes on a bill that they said would be remembered as a landmark achievement.

"What I explained to the president is my district is a difficult district on this," said Rep. Jason Altmire, D-Pa., who received calls from Obama, Emanuel and two Cabinet secretaries. Altmire said he remained undecided.

As rank-and-file members of both parties girded for hours of boisterous floor debate on Saturday, lines began to harden, and attention was focused on Democrats coming out in opposition to the bill, including several centrists from rural districts.

With Democrats controlling 258 of 435 House seats as of Friday, they can afford only 40 of their members breaking ranks and still win approval for the measure.

As of Friday evening, Democratic officials counted just more than 205 certain votes and were hopeful that a successful resolution of the abortion and immigration issues would produce the final commitments to ensure passage of the bill.