(Bloomberg) -- Senate Republicans gave up on theirlast-ditch proposal to repeal Obamacare Tuesday as opposition intheir own ranks ended months of fruitless efforts to gut theAffordable Care Act.

"We don’t have the votes," bill co-sponsor Bill Cassidy ofLouisiana told reporters in Washington. "We’ve made the decision,since we don’t have the votes, we’ll postpone that vote."

The chamber won’t vote before Saturday’s deadline to use afast-track procedure to keep Democrats from blocking a GOP-onlybill. On Monday, Republican Senator Susan Collins of Maine addedher opposition to that of GOP Senators John McCain of Arizona andRand Paul of Kentucky, enough to sink the legislation in the 52-48Senate.

"It’s only a matter of when" the measure will be enacted, saidco-sponsor Lindsey Graham of South Carolina. "We’re coming back tothis after taxes." Senate Republicans plan next to work onlegislation to overhaul the U.S. tax system.

Republicans have campaigned on repealing Obamacare for sevenyears, and they thought their goal was in sight when the GOP tookcontrol of the presidency as well as both houses of Congress inJanuary. While House Republicans passed a bill in May andcelebrated at the White House Rose Garden with President DonaldTrump, their measure wasn’t acceptable to the Senate, which hasbeen unable to agree on a plan of its own.

Senate Majority Leader Mitch McConnell’s own proposal stumbledto an embarrassing 49-51 defeat in July, with McCain providing thefinal "no" vote. The House and Senate proposals were crafted insecret, with no public hearings or input from Democrats.

Trump has repeatedly criticized congressional Republicans forfailing to quickly send a repeal bill to his desk after promisingfor seven years to end the Affordable Care Act. Republicans couldrevive efforts to repeal Obamacare in the next fiscal year startingOct. 1, though it would be much more difficult to do as theirprimary focus will be on overhauling the U.S. tax system.

The Graham-Cassidy proposal would turn Obamacare funds intoblock grants for the states and cut Medicaid funds to states thatexpanded the program under the Affordable Care Act. It would leavemost of the Obamacare taxes in place.