WASHINGTON (Reuters) - U.S. House leaders have decided against holding a vote on a reworked healthcare system overhaul this week after failing to find the necessary support, congressional aides said on Thursday. White House officials had urged a floor vote on the legislation before President Donald Trump’s 100th day in office on Saturday, hoping to follow through on a campaign promise to repeal and replace the 2010 Affordable Care Act, also known as Obamacare. Advocates had hoped to raise enough support for the measure after a group of hard-line Republican conservatives endorsed an amended version on Wednesday. But by Thursday evening Republican leaders still had not collected enough votes from moderate Republicans whose backing was also needed for passage in the House, given united Democratic opposition. “We won’t vote this week,” said one House Republican aide, who asked not to be named. Next week was not ruled out, another indicated. “We’ll call a vote when we have the votes.” Representative Pete Sessions, a senior House Republican, also left the door open to a vote next week. Possibly referring to Trump, Sessions said that a lot of people had tried to rush the legislation to the floor, but House Republican leaders want to “allow the time to do it right. “I said it will find its time and I am satisfied we are moving at a pace, keeping people engaged,” he said at a late night session of the House Rules Committee he chairs. The Republican healthcare bill would replace Obamacare’s income-based tax credit with an age-based credit, roll back an expansion of the Medicaid government health insurance program for the poor and repeal most Obamacare taxes. The nonpartisan Congressional Budget Office had estimated 24 million fewer people would have insurance than under the original version.  House leaders brought the bill to the floor last month after Trump demanded a vote, but yanked it after a rebellion by Republican moderates and the party’s most conservative lawmakers, in a major setback for Trump. An amendment drafted by Representative Tom MacArthur won over conservatives in the hardline Freedom Caucus this week, reviving some hopes that the bill could still pass. The amendment would allow states to seek waivers from some provisions. Among these are one mandating that insurers charge those with pre-existing conditions the same as healthy consumers, and that insurers cover so-called essential health benefits, such as maternity care.      But a number of centrist Republicans still opposed the measure. “Protections for those with pre-existing conditions without contingency, and affordable access to coverage for every American, remain my priorities for advancing healthcare reform, and this bill does not satisfy those benchmarks for me,” Representative Ryan Costello of Pennsylvania said in a statement posted on social network Twitter on Thursday. Some outside groups like the American Medical Association weighed in against the legislation, saying it would cost millions their health care coverage. The bill’s future is further clouded in the Senate. 