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A government shutdown looms as Congress risks missing a key deadline this weekend over the battle in the Senate on a massive 2,000-page catchall spending bill that Republicans have vowed to oppose unless they can strip it of earmarks.

Senate Majority Leader Harry Reid is expected Thursday to take up the $1.27 trillion omnibus spending bill that would fund the government through the end of the fiscal year, to Sept. 30.

But Republicans have threatened to stall debate by forcing the 1,924-page bill to be read aloud in the Senate -- a move that would take 35 to 40 hours and push the debate into Saturday, according to numerous aides.

A temporary stopgap measure currently funding the government is set to expire midnight on Saturday. But a number of procedural steps would prevent the Senate from getting to a final vote until late Monday or early Tuesday.

"It's not our fault," a senior Senate Democratic leadership aide said about a potential government shutdown. The aide argues that Republicans are insisting on obstructing this bill.

Republicans and some Democrats argue that the Senate should follow in the footsteps of the House and pass another temporary spending bill to fund the government at current levels until February, when lawmakers would have time to examine the spending. By then, Republicans will control the House and hold six additional seats in the Senate.

But if President Obama doesn't sign into law either the Democratic-proposed bill or a temporary stopgap measure by Saturday, then the government will close shop.

Senate Minority Leader Mitch McConnell, R-Ky., encouraged his members to reject the bill.

"Americans told Democrats last month to stop what they've been doing: bigger government, 2,000-page bills jammed through on Christmas Eve, wasteful spending," he said on the Senate floor Wednesday morning. "The bill is a monument to all three."

McConnell noted that the bill includes more than $1 billion to fund the new health care law -- a provision that he said by itself is enough to spur Republicans who have vowed to repeal it to oppose the measure.

"It's being dropped on us with just a few days to go before the Christmas break, ensuring that no one in Congress has a chance to examine it thoroughly before the vote," he said. "And ensuring that Americans don't have a chance to see what's in it either. This, too, is reason enough to oppose it."

Thousands of earmark requests -- pet projects of lawmakers -- are listed in the bill, worth about $8 billion.

Sen. John McCain tweeted the top 10 earmarks in the spending bill, including $247,000 for virus free wine grapes in Washington State, $413,000 for peanut research in Alabama, $235,000 for noxious weed management in Nevada and $400,000 for solar parking canopies and plug-in electric stations in Kansas.

McCain expressed disbelief about the projects.

"Are we tone deaf? Are we stricken with amnesia?" he said, adding that voters made it clear in last month's midterm elections that they're tired of business as usual in Washington.

Republican Sens. John Cornyn of Texas and John Thune of South Dakota also objected to the bill, with Cornyn saying the omnibus bill might as well be called "ominous."

Fox News' Trish Turner contributed to this report.