Washington » House Democrats triggered the countdown Monday for the climactic vote on President Barack Obama's fiercely contested remake of the health care system, even though the legislation remained incomplete and lacked the votes needed to pass.

Obama expressed optimism Congress would approve his call for affordable and nearly universal coverage as he pitched his plan on a trip to Ohio, and congressional leaders showed signs of progress in winning anti-abortion Democrats whose votes are pivotal.

At the same time, Sen. Jim DeMint, R-S.C., among the bill's sharpest opponents, said he was "less confident" than before that it could be stopped.

"They'd have to be remarkable people not to fall under the kind of pressure they'll be under," he said of rank-and-file Democrats.

Some of the pressure was aimed at Rep. Dennis Kucinich, D-Ohio, who flew aboard Air Force One with President Barack Obama during the day, then walked into a senior citizen center with the chief executive in time to hear a voice from the audience yell out, "Vote yes."

A smiling Obama turned to the liberal lawmaker and said, "Did you hear that, Dennis?" Then, turning back to the audience, he added, "Go ahead, say that again."

"Vote yes!" came back the reply.

Kucinich, who said he remains uncommitted, is one of 37 Democrats currently in the House who voted against Obama's legislation when it cleared the House last fall.

In addition, the White House is laboring to hold the support of several other Democrats who voted for the earlier bill, but only after first supporting strict anti-abortion limits that would be altered the second time around.

"When we bring the bill to the floor, then we will have the votes," said Speaker Nancy Pelosi.

Outside interests on both sides sought to prevail on wavering lawmakers.

The National Right to Life Committee, which opposes abortions, wrote to lawmakers that support for the Senate bill would be a "career-defining pro-abortion vote."

Union groups and other supporters announced a $1.3 million advertising campaign urging 17 House Democrats to vote for the measure, and officials at the Service Employees International Union threatened to withdraw support from Democrats who vote against the bill if it loses.

The lobbying came as the House Budget Committee, on a 21-16 vote, took an essential first step toward the House vote, which could come by the weekend.

It was more than a year ago that Obama asked Congress to approve legislation extending health coverage to tens of millions who lack it, curbing industry practices such as denying coverage on the basis of pre-existing medical conditions, and beginning to slow the growth of health care nationally. His plan would require most Americans to buy health insurance, fine most who fail to do so and provide government subsidies to help middle-income earners and the working poor afford it.

Sweeping legislation seemed to be on the brink of passage in January, after both houses approved bills and lawmakers began working out a final compromise in talks at the White House. But those efforts were sidetracked when Republicans won a special election in Massachusetts -- and with it, the ability to block a vote on a final bill in the Senate.

Now, nearly two months later, lawmakers have embarked on a two-step approach that requires the House to approve the measure passed by the Senate, despite misgivings on key provisions. That would be followed by both houses quickly passing a second bill that makes changes to the first. In the Senate, that second bill would come to a vote under rules that deny Republicans the ability to filibuster.

The details of the second, fix-it measure were closely guarded -- and subject to last-minute changes. In general, officials have said they would provide more money for lower-income families unable to afford health care and states that already provide above average coverage for the poor under Medicaid, as well as improved prescription drug coverage under Medicare.

The cost of the overhaul is expected to total $950 billion or more over a decade.