WASHINGTON – The seven-year Republican quest to undo the Affordable Care Act appeared to reach a dead end on Tuesday in the Senate, leaving President Donald Trump vowing to let President Barack Obama's signature domestic achievement collapse.

Trump declared that his plan was now to "let Obamacare fail," saying Democrats would then seek out Republicans to work together on a bill to bury the Affordable Care Act. If he is determined to make good on that pledge, he has plenty of levers to pull, from declining to reimburse insurance companies for reducing low-income customers' out-of-pocket costs to failing to enforce the mandate that most Americans have health coverage.

"It'll be a lot easier," Trump said at the White House, adding: "We're not going to own it. I'm not going to own it. I can tell you the Republicans are not going to own it. We'll let Obamacare fail, and then the Democrats are going to come to us."

The fate of the repeal effort looked to be sealed on Tuesday, when a last-ditch attempt to force a vote to abolish the health law without a replacement came up short of support. The majority leader, Sen. Mitch McConnell of Kentucky, seemed resolved to force senators to vote next week, but by Tuesday afternoon, it was clear he did not have 50 votes even to clear a procedural hurdle before considering a repeal-only bill.

Sens. Shelley Moore Capito of West Virginia, Susan Collins of Maine and Lisa Murkowski of Alaska, all Republicans, declared that they would not vote to repeal the Affordable Care Act without a replacement: enough to doom the effort before it could gain any momentum. Sen. Rob Portman, R-Ohio, also rejected a repeal-only measure.

The collapse highlighted a harsh reality for Senate Republicans: While they freely assailed the health law when Obama occupied the White House, they could not come up with a workable plan to unwind it that would keep both moderate Republicans and conservatives on board. It was an enormous embarrassment for a party that rode electoral waves to control first the House, then the Senate and then the White House, but has not been able to deliver a major legislative victory.

"This has been a very, very challenging experience for all of us," McConnell said. "Everybody's given it their best shot, and as of today, we just simply do not have 50 senators who can agree on what ought to replace the existing law."

Trump has considerable leverage to gum up the works of the Affordable Care Act. He could throw insurance markets into a tailspin at any time by cutting off the reimbursement payments to insurers, as he has threatened to do. He could further destabilize the markets by not enforcing the mandate that most Americans have health insurance.

And he could cancel advertising and other efforts to encourage enrollment under the Affordable Care Act when the annual sign-up period begins in November. A barrage of negative statements from the administration could project an official view that the health law is collapsing, creating a self-fulfilling prophecy.

The lack of certainty over the so-called cost-sharing reduction payments, which go toward reducing out-of-pocket costs for low-income people, has been a major concern for insurers. The companies say premiums will be significantly higher without the funding, and some companies that have submitted rates to sell insurance in the market next year could decide to pull out.

"With open enrollment for 2018 only three months away, our members and all Americans need the certainty and security of knowing coverage will be available and affordable for them," said Justine Handelman, a senior executive at the Blue Cross Blue Shield Association.

While Trump has promised destruction, other Republicans signaled that they wanted to take a more constructive approach. Sen. Lamar Alexander of Tennessee, chairman of the Senate health committee, announced that he would hold hearings in the next few weeks on stabilizing the individual health insurance market.

Members of both parties have ideas about how to secure insurance markets and hold down premiums. One possible action is to provide money for the reimbursement payments. Two Democratic senators, Tom Carper of Delaware and Tim Kaine of Virginia, want the federal government to help pay the largest claims through a backstop known as reinsurance. Senators of both parties also want to help consumers in counties where no insurer chooses to offer health plans through the Affordable Care Act marketplace — a real possibility in some places next year.

The Senate Democratic leader, Chuck Schumer of New York, implored Republicans to defy Trump and work with Democrats to strengthen insurance markets.

"There's a fork in the road for our Republican colleagues," he said. "They can do what Donald Trump said, which is sabotage the system out of anger and out of pique," or they can work with Democrats on improvements to the health law.

"Whether they can resist Trump, I don't know," Schumer said.