(Reuters) - The Senate on Wednesday approved legislation to avert a government shutdown next week, freeing Democrats and Republicans to spend the next few months arguing over deeply divided strategies to shrink longer-term budget deficits.

The bill, which would keep government agencies and programs funded through the end of the fiscal year on September 30, must go back to the House of Representative for final approval on Thursday.

House Appropriations Committee Chairman Hal Rogers said he was pleased with the bill and believes it can pass the Republican-controlled House.

"It's a great success," Rogers told reporters. He called the effort a "healthy start" toward returning to a normal, bipartisan budgeting process.

The measure, approved by a 73-26 vote, keeps in place $85 billion in automatic spending cuts, but it offers the military and some domestic agencies more flexibility to shift funds within these reduced budgets to higher-priority programs.

Without new government spending legislation enacted by March 27, federal agencies and discretionary programs ranging from the Department of Transportation to national parks would have faced a shutdown.

Both parties opted against risking such a shutdown as they wrangle over longer-term tax and spending policy. If approved by the House as expected, the measure pushes the next critical fiscal deadline to late July or early August, when the next increase in the federal borrowing limit will be needed.

Until then, Democrats and Republicans are likely to argue over their vastly different budget resolutions that are expected to pass each chamber before a two-week recess starts at the end of the week.

The Senate immediately opened debate on its first budget in nearly four years, a Democratic-focused plan that calls for raising nearly a $1 trillion in new tax revenues, spending $100 billion more on infrastructure and offering up some modest spending cuts.

The Senate budget stands in stark contrast to the Republican proposal being debated in the House, which calls for deep cuts to social programs to reach a small surplus by 2023.

Some analysts question whether the House and Senate will be able to reconcile their diametrically opposed budgets and say a broader fiscal agreement would require direct negotiations this summer between President Barack Obama and House Republicans.

That scenario could be eerily reminiscent of the high-pressure 2011 budget standoff, in which a deal was cobbled together before a potential August debt default.

The budget blueprints do not carry the force of law, but set a guideline for an overall spending limit for discretionary budgets determined by the appropriations committees.

PET PROJECTS

The Senate vote was not without drama. Dozens of senators tried to attach provisions to shield pet programs and regional interests from the pain of automatic spending cuts ranging from air traffic controllers to inspectors at meat processing plants.

On Tuesday, Republican Senator Jerry Moran of Kansas tried to block Senate consideration of the spending bill for the rest of this fiscal year unless he was promised a vote on his proposal to shield air traffic controllers at small, rural airports from the spending cuts.

Moran's sparsely populated state depends heavily on small airports and is home to several civil aircraft manufacturers. He said staff reductions or shutdowns of rural control towers would remove a critical safety layer in the air traffic control system.

"Once there is an accident, and somebody dies and a plane crashes, the question will always be 'what if there had been an air traffic control tower there? What if we had left the program in place?'" Moran told the Senate.

Moran's amendment was not considered, but the Senate approved a proposal to shift about $55 million in U.S. Department of Agriculture funds to prevent temporary layoffs of meat inspectors.

A plan to shift some national park-related funding to keep White House tours open in the face of cuts was defeated.