WASHINGTON (AP) — Senate Republicans unveiled a budget plan Friday that lays the groundwork for their effort to overhaul the nation's tax system, the top legislative priority for President Donald Trump and the GOP.

House and Senate passage of the budget blueprint is required in order to allow Republicans to pass follow-on tax legislation this year. The ambitious tax plan would lower rates for businesses and individuals. Trump described it Friday as a "giant, beautiful, massive, the biggest ever in our country, tax cut."

The Senate Budget Committee plans to vote on its plan next week. A companion measure is headed for a House vote next week as well.

The new budget plan would permit the upcoming tax measure to add $1.5 trillion over the coming decade to the $20 trillion national debt.

The two-step process is the only way, under congressional rules, for the tax package to pass through the Senate without fear of Democrats blocking it with a filibuster. Republicans used the same process earlier this year in failed attempts to repeal the Affordable Care Act.

Without the budget passage, Senate Majority Leader Mitch McConnell of Kentucky said in a statement, "Democrats will continue to play partisan politics and obstruct our efforts to get our economy flourishing and growing at its full potential."

More broadly, the Senate plan promises a balanced budget over the coming decade, but it relies on rosy projections of economic growth and spending cuts that Republicans have no plans to deliver. It would keep Pentagon spending mostly frozen at current levels, rather than the almost $90 billion increase demanded by GOP military hawks.

The budget also contains a provision that could allow the Senate to approve legislation opening up drilling in the Arctic National Wildlife Refuge. That's a longtime goal for Republicans including Alaska Sen. Lisa Murkowski, a moderate whose vote will be needed on tax legislation.