* President hopes lunch will strengthen Republican resolve
* Doubts about repeal vote next week
* Senator hopes Trump will be more forceful
* Bipartisan fixes for Obamacare pushed by Democrats (Adds Trump quotes)
WASHINGTON, July 19 (Reuters) - U.S. President Donald Trump scolded Senate Republicans on Wednesday for failing to reach agreement on repealing or overhauling Obamacare, demanding they keep their campaign promises and find a new healthcare approach.
Trump told 49 senators who came to a White House lunch that they should not leave Washington for a planned August recess until they can find common ground on healthcare.
"We're close. We're very close," Trump said at the start of the lunch meeting, a day after the seven-year Republican quest to repeal and replace Democratic former President Barack Obama's signature healthcare law seemed to collapse in the Senate.
"For seven years you promised the American people you would repeal Obamacare. People are hurting and, frankly, inaction is not an option," Trump told the Republican lawmakers. "Any senator who votes against starting debate is really telling America that you're fine with Obamacare."
Senate Majority Leader Mitch McConnell has vowed to go ahead with a vote early next week on a repeal of the Affordable Care Act, popularly known as Obamacare, despite indications it will fail after the defections on Tuesday of at least three Republican senators.
Moderate Republican senators Susan Collins of Maine, Lisa Murkowski of Alaska and Shelley Moore Capito of West Virginia said they oppose McConnell's plan for a repeal that would take effect in two years, giving Congress time to develop a replacement. All three attended the lunch.
With Democrats united in opposition to repeal, McConnell can only lose two votes from his 52-48 majority in the 100-seat Senate to pass healthcare legislation.
Trump, who had not been heavily involved in lobbying the Senate on the issue until this week, said he wanted more than a straight repeal vote and wanted the Senate to pass a replacement measure as well.
"We can repeal, but we should repeal and replace and we shouldnt leave town until this is complete," he said.
Capito, speaking to reporters ahead of the meeting on Wednesday, expressed some doubts the Senate vote on a repeal-only healthcare bill would actually occur next week. "Its changing so quickly," she said.
"I think we're probably going to air what our differences are again. The president has taken a lot of time to try to call us all individually," said Capito. "I don't think anyone's mind is going to get changed sitting right there, but it gives us a chance to frame it where we have our differences."
'HONOR OUR PROMISE'
Repealing and replacing Obamacare was a top campaign promise for Trump and Republicans in Congress, who say it is a costly intrusion into the healthcare system.
But the reality has been difficult for a party divided between moderates concerned the Senate bill would eliminate insurance for millions of low-income Americans and conservatives who want to see even deeper cuts to Obamacare, which boosted the number of Americans with health insurance through mandates on individuals and employers, and income-based subsidies.
"We have to honor our promise," Republican Senator Ted Cruz told reporters. "For seven years Republicans have told the voters, if you elect us, well repeal Obamacare. I think we will look like fools if we cant deliver on that promise."
Republican Senator Orrin Hatch said it was a tough issue for Trump, but "I suspect he could be a little bit more forceful and I hope he will be. I think he needs to."
Democrats, clearly delighted with the turn of events, have welcomed the Republicans' failure to replace Obamacare as an opportunity to work together. Republicans conceded their other options may be exhausted.
The No. 2 Senate Republican, John Cornyn, told reporters it was "unfortunate" that he expected bipartisan talks to begin.
"Democrats are strongly committed to Obamacare and are unwilling to admit structural problems, which create the problems we are having in the individual market today," Cornyn said. "But we'll do the best we can with the hand we've been dealt."
If senators try to shore up Obamacare, an initial hurdle in coming weeks will be boosting faltering state insurance markets by ensuring that insurers keep receiving subsidies that help lower the cost of insurance for low-income individuals.
The Trump administration will continue making the subsidy payments through August while a related Republican lawsuit is pending. The uncertainty beyond that has rattled insurers.
Republican senators have acknowledged the need to address the unstable markets but resisted Democratic calls to fund the subsidies without accompanying reforms, calling it a "bailout" for insurance companies.
Funding for the Children's Health Insurance Program, a part of the Medicaid government health insurance program for the poor and disabled, known as CHIP, expires on Sept. 30 and will require reauthorization.
Bills to address the subsidy payments and CHIP would likely require 60 votes for passage, acting as a barometer of how inclined Republicans and Democrats are to work together, industry lobbyists and experts said.
Trump suggested on Tuesday that Republicans should allow the insurance markets to fail before working with Democrats. But Republican Senator Lamar Alexander, the head of the Senate Committee on Health, Labor and Pensions, said he would begin holding hearings on the issue in the next few weeks. (Writing by John Whitesides; Additional reporting by Susan Cornwell, Richard Cowan, Yasmeen Abutaleb and Susan Heavey; Editing by Jonathan Oatis and Nick Zieminski)