WASHINGTON (Reuters) -After days of delay, U.S. congressional leaders unveiled a $1.2 trillion bipartisan spending measure for defense, homeland security and other programs early on Thursday, giving lawmakers less than two days to avert a partial government shutdown.

The Republican-controlled House of Representatives will vote on the sprawling package on Friday, leaving the Democratic-majority Senate only hours to pass the package of six bills that covers about two-thirds of the $1.66 trillion in discretionary government spending for the fiscal year that began on Oct. 1.

Democratic Senate Majority Leader Chuck Schumer wasted no time in urging his fellow senators to act quickly once the legislation arrives from the House.

Since the fiscal year began on Oct. 1, Congress has had to pass four temporary funding bills to avert government shutdowns because of unresolved battles over spending priorities and the size of annual appropriations.

"Once the House acts the Senate will need bipartisan cooperation to pass it before Friday's deadline and avoid a shutdown," Schumer said in a Senate speech.

The Congressional Budget Office warned that U.S. deficits and debt will grow considerably over the next 30 years, forecasting that the nation's $34.5 trillion national debt, which currently represents about 99% of GDP, could grow and rise to 166% of GDP by 2054.

Ratings agencies have also warned that Congress's repeated brinkmanship could hurt the U.S. government's creditworthiness.

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The compressed schedule raised the risk of at least a brief partial shutdown after a Friday midnight deadline. Any one senator can erect procedural hurdles to slow final passage of the 1,012-page bill.

"There will be no time to read the text, to vet it with our staffs and our constituents, to debate the bill and offer amendments to improve the bill," said conservative Republican Senator Mike Lee, as he criticized the wide-ranging bill.

House Speaker Mike Johnson touted what he called a series of wins for Republicans, from higher spending for U.S. defense and border security to a cutoff of U.S. funding for the main United Nations relief agency that provides humanitarian assistance to Palestinians in Gaza.

"This FY24 appropriations legislation is a serious commitment to strengthening our national defense by moving the Pentagon toward a focus on its core mission," Johnson said in a statement released along with the text of the legislation.

Democrats said they blocked some Republican cuts and policy measures and touted funds aimed at lowering childcare costs, supporting small businesses and fighting the flow of the opioid fentanyl.

"We defeated outlandish cuts that would have been a gut punch for American families and our economy - and we fought off scores of extreme policies that would have restricted Americans' fundamental freedoms," said Senator Patty Murray, the Democratic chair of the Senate Appropriations Committee.

With a slim 219-213 House Republican majority, Johnson will have to rely on Democratic votes to pass the bill.

Besides the departments of Homeland Security and Defense, the bill would fund agencies including the State Department and the Internal Revenue Service as it girds for its April 15 taxpayer filing deadline.