WASHINGTON, United States (AFP) - Efforts by the House of Representatives to end the United States debt ceiling showdown hit snag after snag on Tuesday as it remained unclear if the Republican leadership's measures could pass the chamber.

House Speaker John Boehner's team unveiled a stripped-down Republican bill extending the US debt ceiling until Feb 7 and funding government for the next two months.

But a rules committee postponed a key hearing that would allow the bill to reach the floor.

"The House will vote tonight to reopen the government and avoid default," House Speaker John Boehner's spokesman Michael Steel said late into a rollercoaster day in Congress, where Republicans could not close ranks behind an earlier proposal.

The new 11th-hour plan comes 15 days into a government shutdown, and barely 30 hours before the US hits a deadline when it will start running out of funds to pay its bills.

It leaves extraordinarily little wiggle room for the Senate to make any changes to the bill, as its Democratic leadership would likely move to do, before running up against Thursday's debt ceiling deadline.

And with the Rules Committee postponing its hearing that would permit a same-day vote, the entire Republican House plan - and the congressional outcome - was being thrown into question.

Mr Boehner's team had made some substantial changes to the measure, including stripping out provisions that would have delayed two taxes that help fund President Barack Obama's health care law.

It also shortens the stopgap spending period to Dec 15, instead of Jan 15 which was in the earlier plan, so that Republican lawmakers can take another shot at removing an "Obamacare" provision known as the contraception mandate before it goes into force in 2014.

"It boils down to conscience protections that basically become compromised on the 1st of January. That's bothersome to a lot of people," Republican congressman Steve Womack said after a meeting with House leadership.

The clause would exempt employers from having to provide coverage for birth control as part of the health care plans they offer employees, something long-sought by Republicans.

The new bill would also eliminate health insurance subsidies for employees it compels to be under the health care law, including the president and his cabinet, members of Congress and their staff.

Democrats argue that the measure, first proposed by Republican Senator David Vitter, would merely strip away the employer health care contribution from staffers, but Republicans insisted it eliminates special treatment for Congress and the White House under "Obamacare."

"It's a simple message, it's one that our conference can rally behind," Mr Womack told reporters.

The measure also remove a president's long-held authority to use "extraordinary measures" that extend the time that Treasury can keep paying the nation's bills after the US bumps up against its borrowing limit.

Womack and moderate House Republican Devin Nunes said they believed the latest measure had the votes to pass the House, but the rules committee postponement made that far less clear.

It would also likely be changed in the Democrat-led Senate, where bipartisan negotiations have been put on hold to see what the House brings forth.

Senate Majority Leader Harry Reid, who has held days of face-to-face negotiations with his Republican counterpart Mitch McConnell, declared the earlier House measure a blatant attempt to "torpedo the Senate's bipartisan progress." "Let's be clear: the House legislation will not pass the Senate," Mr Reid said.