Washington - With federal agencies set to close their doors in five days, House Republicans began exploring a potential detour on the path to a shutdown: shifting the fight over President Barack Obama's health care law onto a separate bill that would raise the nation's debt limit.

If it works, the strategy could clear the way for the House to approve a simple measure to keep the government open into the new fiscal year, which will begin Tuesday, without hotly contested provisions to defund the Affordable Care Act.

However, it would set the stage for an even more nerve-wracking deadline on Oct. 17, with conservatives using the threat of the nation's first default on its debt to force the president to accept a one-year delay of the health care law's mandates, taxes and benefits.

Obama administration officials dismissed the plan, vowing that there would be no delay of the insurance initiative, which is set to begin enrolling consumers Tuesday. They argued that Republicans risk destroying their own credibility among voters, who strongly disapprove of such brinksmanship regardless of their views on the Affordable Care Act.

"Once you start saying 'delay' with something as damaging as the default of the United States, people hear the second part: They hear the default," said White House strategist David Simas, speaking at a breakfast held by Third Way, a moderate Democratic group.

GOP leaders met for nearly 90 minutes Wednesday afternoon to discuss the strategy, which they plan to present to rank-and-file lawmakers this morning. If it wins approval, the leaders hope to introduce the debt-limit bill today and hold a vote as soon as Saturday - letting GOP lawmakers mount a fresh assault on the health care law before deciding whether to shut down the government.

The debt-limit bill will be loaded with dozens of other conservative priorities, including the approval of the Keystone XL oil pipeline and the abolition of the new Consumer Financial Protection Bureau.

Rep. Steve Southerland of Florida, who attended the meeting on behalf of the massive class of GOP lawmakers elected in 2010, sidestepped questions about whether conservatives would be willing to trade the leverage of a government shutdown for the leverage of a default.

Leaders are "running the traps on every conceivable formula," he said. "We're looking at every possibility."

The strategizing in the House came as Senate Democrats advanced a slow but inevitable campaign to approve a measure to keep the government open without undermining the president's most significant legislative achievement, the Affordable Care Act, derided by critics as Obamacare.

After conservative Rep. Ted Cruz, R-Texas, staged a 21-hour attack on the law, he joined all 99 of his Senate colleagues Wednesday in voting to end his filibuster and start debating a House-passed bill that would fund the government through Dec. 15.

As written, that measure also would defund Obamacare. But after a long debate expected to stretch into the weekend, Senate rules permit Majority Leader Harry Reid, D-Nev., to strip out the anti-Obamacare provisions, change the expiration date on the funding bill to Nov. 15 and pass the measure with a simple majority achieved entirely with Democratic votes.

With passage of the funding bill all but certain, Cruz's talkathon accomplished little. The Senate is expected to approve the bill Saturday. That would give House Speaker John Boehner, R-Ohio, barely 24 hours to pass the Senate version or respond with add-ons.

Among the options: repeal a tax on medical devices that was adopted to help finance the health initiative but has never been popular in either party; abolish insurance subsidies that members of Congress and their staffs receive from their employer, the federal government; or even delay the health care law's requirement that every individual purchase insurance, known as the individual mandate.

But any move to change the bill in the House, no matter how noncontroversial, would require another vote in the Senate, virtually guaranteeing a shutdown. Both chambers must agree on a funding plan by midnight Monday to keep federal agencies open Tuesday.

That leaves approval of the Senate bill as Boehner's best bet for avoiding a shutdown. And the evolving debt-limit bill could help.

The debt-limit measure, which was still receiving new provisions late Wednesday, amounts to a grand conservative wish list. In addition to delaying implementation of the health care law for one year, the bill would establish a timetable for tax reform, squeeze $120 billion from federal health programs over the next decade - in part by tightening medical malpractice laws - and cut federal civil-service pensions.

The measure also would approve construction of the Keystone XL oil pipeline and advance other GOP economic goals, including increasing offshore oil drilling, blocking federal regulation of greenhouse gas emissions and restricting most forms of federal industry regulation.

About the only major piece of the Republican agenda missing from the bill is a ban on late-term abortions - and some lawmakers who oppose abortion were arguing to add that, GOP aides said.

By stuffing the bill with so many appealing provisions, GOP leaders hoped to persuade at least 217 Republicans to support its sole negative aspect: raising the $16.7 trillion federal debt limit through Dec. 31, 2014 - an increase worth about $1.1 trillion, by independent estimates.

If the House passes the measure, GOP leaders could argue that it should become the new weapon for continuing the assault on the Affordable Care Act, allowing Republicans to abandon the fight against the government funding bill.

It was unclear late Wednesday whether that strategy would work. Rep. Pete Sessions, R-Texas, a close Boehner ally, told reporters only that the debt legislation would be introduced "very soon."

Meanwhile, White House officials scoffed at the strategy, with senior adviser Dan Pfeiffer tweeting that the plan "goes nowhere" and leaves Republicans "responsible for massive econ calamity."

Added Simas, the White House political strategist: "What the American people will hear and see is that you have a minority within a party, and this is a minority within the Republican Party who are not listening to the more reasonable elements in the party, and they are willing to risk the full faith and credit of the United States of America and plunge the country into default because of their obsession with denying health insurance to 11 million Americans."

As the standoff continued on Capitol Hill, White House officials were pressing ahead with the rollout of the health care initiative, even as they played down expectations that huge numbers of Americans would sign up for insurance right away. As happened when Massachusetts implemented its universal coverage plan, Simas predicts that Americans will sign up in spurts mainly just before coverage begins in January, and again right before enrollment ends in March.

But enrollment will be up and running Tuesday even if the rest of the government shuts down, Simas said. Eighty-five percent of the Affordable Care Act's funding comes from accounts that would not be affected by a shutdown.