WASHINGTON — With the fate of his signature legislative initiative far from certain, President Barack Obama is taking his last-ditch push for health care reform on the road.

In a speech Monday in Philadelphia, Obama will try to persuade the public to back his plan to remake the nation's health care system, while also urging uneasy lawmakers to cast a "final vote" for a massive reform bill in an election year.

Obama's pitch in Philadelphia, along with a stop in St. Louis Wednesday, comes as the president begins an all-out effort to pass his health care proposals. Though his plan has received only modest public support, Obama has implored lawmakers to show political courage and not let a historic opportunity slip away.

Despite staunch Republican opposition, Democratic leaders are cautiously optimistic they can pass a bill without GOP votes.

"I think the trend is in the right direction because people see that the status quo is absolutely broken," Rep. Chris Van Hollen, D-Md., said Sunday on CNN's "State of the Union".

Party leaders are narrowing in on a strategy that calls for House Democrats to go along with a health care bill the Senate passed in December. Obama would sign it into law, but senators would promise to make numerous changes on issues that have concerned House Democrats. Because Senate Democrats lost the 60-seat majority needed to stop GOP filibusters with the Massachusetts Senate race, the changes would have to be made under rules that require only simple majority votes.

That strategy would put lawmakers on way to meet Obama's goal of Congress passing a health care bill by March 18, when he leaves on a trip to Indonesia and Australia. White House spokesman Robert Gibbs said Obama would sign a bill "shortly thereafter."

But full Democratic support is far from certain. Some party moderates are uneasy about the cost of the $1 trillion bill and its language on abortion, and some House Democrats are suspicious of whether their Senate colleagues would follow through on promises to work out the differences in the bills.

"The Senate has given us a lot of reason not to trust them," Rep. Jason Altmire, D-Pa., said on Fox News Sunday. "There has to be some certainty that the Senate is going to follow through on their part."

The Democratic plan includes greater consumer protections and a ban on discriminating against customers with pre-existing conditions. Small businesses also would receive a tax credit this year. The White House hopes the immediate changes created by the bill would give Democratic candidates a strong platform on which to campaign in the fall.

Though Obama has included some GOP proposals in his plan, Republicans have called for the existing bills to be scratched and for the process to start anew. Party leaders insist they're on the side of an American public that doesn't want the government-controlled health care they maintain the president's plan would create.

"The American people are saying to us, stop this job-killing health care bill. We know it will drive taxes up and that will not be good to help us get out of the recession," Senate Minority Leader Mitch McConnell said Sunday on ABC's "This Week."

The Obama administration and its allies are continuing to pressure the health insurance industry as it underscores the president's calls to pass a health care overhaul urgently.

Days after meeting with representatives from the nation's leading insurers, Health and Human Services Secretary Kathleen Sebelius was to send executives a letter Monday reiterating her request that companies publicly justify proposed rate hikes that have infuriated customers.

In the letter obtained by The Associated Press, Sebelius asks the executives to post their justifications online, including detailed descriptions of costs and the number of consumers affected by the increases.

On Tuesday, a coalition of labor unions and activist groups under the umbrella of Health Care for America Now are planning what they've billed as a "massive protest" at the health insurance industry's annual Washington policy conference.

Supporters plan to march on the downtown hotel hosting the conference to attempt a symbolic "citizens' arrest" of insurance industry representatives meeting inside, according to the groups' press release. The activists have asked prominent Washington insiders who had agreed to speak at the America's Health Insurance Plans conference to cancel.

On Wednesday, the group will be on Capitol Hill with people who have had bad encounters with insurance companies and will tell their stories to lawmakers.

Associated Press writers Ricardo Alonso-Zaldivar and Erica Werner contributed to this report.

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