WASHINGTON - U.S. House Speaker Mike Johnson's plan to avert a government shutdown faces a key test on Tuesday, as he tries to overcome hardline opposition from his own Republican conference, even as some Democrats signal tentative support for the measure.

Johnson, who had little senior congressional leadership experience before being elected speaker less than three weeks ago, is trying to muster Republican support for a "clean" two-step continuing resolution, or "CR," that would keep federal funding levels unchanged into early next year.

To avert a fourth shutdown in a decade, the Republican-controlled House and Democratic-led Senate must agree on a CR that President Joe Biden can sign into law before current funding for federal agencies expires on Friday.

House Republicans hope to vote on Tuesday on the measure to avoid a shutdown that would disrupt pay for up to 4 million federal workers, close national parks and hobble everything from financial oversight to scientific research.

Senate Majority Leader Chuck Schumer, Congress' top Democrat, gave a tentative welcome to the proposal on Monday.

"For now, I am pleased that Speaker Johnson seems to be moving in our direction by advancing a CR that does not include the highly partisan cuts that Democrats have warned against," Schumer said.

But House Republican hardliners are threatening to use procedural roadblocks to stop the bill from advancing.

"This is the wrong approach," said Representative Chip Roy, who told reporters he would block debate on the bill to prevent it from passing with bipartisan support despite "a whole lot of opposition" from Republicans.

Roy and other hardliners criticize the measure for lacking spending cuts and conservative policies, such as tighter U.S.-Mexico border security, and because it would extend food assistance for poor families to Sept. 30.

Congress is in its third fiscal standoff this year, following a months-long spring impasse over the more-than-$31 trillion in U.S. debt, which brought the federal government to the brink of default.

The ongoing partisan gridlock, accentuated by fractures within the narrow 221-212 House Republican majority, led Moody's late on Friday to lower its credit rating outlook on the U.S. to "negative" from "stable," as it noted that high interest rates would continue to drive borrowing costs higher. The nation's deficit hit $1.695 trillion in the fiscal year ended Sept. 30.

'BIPARTISANSHIP IS THE ONLY WAY'

The Senate on Monday paused its plan to move forward on its own CR to allow the House to move first, with Schumer saying "bipartisanship is the only way to avoid a government shutdown."

Johnson's bill would extend funding for military construction, veterans benefits, transportation, housing, urban development, agriculture, the Food and Drug Administration and energy and water programs through Jan. 19. Funding for all other federal operations - including defense - would expire on Feb. 2.

With a slim 221-213 majority, the Republican speaker can afford to lose no more than three party votes on legislation that Democrats oppose.

But at least eight Republicans, most of them on the party's hard right, have vowed to oppose his measure. They claim the bill also leaves in place policies favored by prominent Democrats including Senate Majority Leader Chuck Schumer and Representative Nancy Pelosi, the former House speaker.

"I strongly oppose the proposed 'clean' CR. We simply cannot continue funding Joe Biden, Chuck Schumer, and Nancy Pelosi's radical policies and bloated spending levels," Republican Representative Andrew Clyde said on the social media platform X.

House Republicans will debate the measure behind closed doors on Tuesday morning, and the outcome could determine how and when Johnson moves forward with the CR. He is under party pressure to garner the 218 Republican votes needed to pass the CR before it comes to the floor.

Lawmakers are at odds over discretionary spending for fiscal 2024. Democrats and many Republicans want to stick to the $1.59 trillion that Biden and McCarthy set in their debt ceiling agreement earlier this year. Hardliners have pushed for a figure $120 billion lower. In recent days, they have signaled a net willingness to compromise.

But the political fracas is focused on just a fraction of the total U.S. budget, which also includes mandatory outlays for Social Security and Medicare. Total U.S. spending topped $6.1 trillion in fiscal 2023. REUTERS