WASHINGTON - House Republican leaders have postponed voting on a bill to fund the government and avoid a partial shutdown due to a health care impasse.

Congress needs to pass a new spending bill by the end of the month or the U.S. will run out of money. Lawmakers must also raise the nation's borrowing limit by this fall, or the government won't be able to pay its bills.

At the center of the political gridlock is Obamacare. Some conservative Republicans want the controversial health care law de-funded, and they're willing to use fiscal fights on Capitol Hill to do it, even risking a shutdown.

Under the law, many low- and middle-income families that don't get health insurance through work will be eligible for subsidies to help buy insurance through state-based exchanges. However, Republicans argue that there aren't enough safeguards to prevent fraud.

Any attempt to block the law in the Republican-controlled House would fail in the Democrat-controlled Senate, and the White House fears that battle will ultimately hurt the economy.