WASHINGTON -- Across-the-board spending cuts all but certain, Republicans and Democrats in the Senate are staging a politically charged showdown designed to avoid public blame for any resulting inconvenience or disruption in government services.

The two parties drafted alternative measures to replace the cuts, but officials conceded in advance the rival measures were doomed.

At the White House, President Barack Obama invited congressional leaders to discuss the issue with him on Friday - deadline day for averting the cuts, which would slash $85 billion from the military and domestic programs alike.

Democrats controlling the Senate are pushing a $110 billion plan that would block the cuts through the end of the year. They would carve 5 percent from domestic agencies and 8 percent from the Pentagon but would leave several major programs alone, including Social Security, Medicaid and food stamps, while limiting the cuts to Medicare to a 2 percent reduction to health care providers like doctors and hospitals.

The Democratic plan proposes $27.5 billion in future-year cuts in defense spending, elimination of a program of direct payments to certain farmers, and a minimum tax rate on income exceeding $1 million as the main elements of an alternative to the immediate and bruising automatic cuts, known in Washington-speak as a "sequester."

Republicans were sure to kill the Democratic alternative with a filibuster. They were poised to offer an alternative of their own that would give Obama the authority to propose a rewrite to the 2013 budget to redistribute the cuts. Obama would be unable to cut defense by more than the $43 billion reduction that the Pentagon faces and would be unable to raise taxes to undo the cuts.

The idea is that money could be transferred from lower-priority accounts to accounts funding air traffic control or meat inspection. The White House says such moves would offer only slight relief, but they could take pressure off Congress to address the sequester.

Democrats are sure to vote the GOP measure down. Both the House and the Senate are set to send their members home Thursday afternoon, even as the deadline to avoid the cuts looms the next day. Though bound to fail, the rival votes will allow both sides to claim they tried to address the cuts even as they leave them in place and exit Washington for a long weekend.

Obama on Wednesday summoned top congressional leaders for a White House meeting on Friday. Given longstanding, intractable differences over Obama's insistence that new tax revenues help replace the cuts, the meeting was not expected to produce a breakthrough.

Another topic for Friday's discussion is how to avoid Washington's next crisis, which threatens a government shutdown after March 27, when a six-month spending bill enacted last year expires.

Republicans are planning for a vote next week on a bill to fund the day-to-day operations of the government through the Sept. 30 end of the 2013 fiscal year, while keeping in place the $85 billion in automatic cuts.

The need to keep the government's doors open and lights on - or else suffer the first government shutdown since 1996 - requires the GOP-dominated House and the Democratic-controlled Senate to agree. Right now they hardly see eye to eye.

The House GOP plan, unveiled to the rank and file Wednesday, would award the Pentagon and the Veterans Affairs Department with their line-by-line budgets, for a more-targeted rather than indiscriminate batch of military cuts.

But it would deny domestic agencies the same treatment, which has whipped up opposition from veteran Democratic senators on the Appropriations Committee. Domestic agencies would see their budgets frozen, which would mean no money for new initiatives such as cybersecurity or for routine increases for programs such as low-income housing.

"We're not going to do that," said Sen. Tom Harkin, D-Iowa. "Of course not."

By freezing budgets for domestic agencies, the Republican plan would also deny additional money to modernize the U.S. nuclear arsenal and to build new Coast Guard cutters. GOP initiatives such as more money for the Small Business Administration or fossil fuels research would be hurt as well, but there's little appetite for the alternative, which is to stack more than $1 trillion worth of spending bills together for a single up-or-down vote.

The GOP move to add the line-by-line spending bills for the Pentagon and veterans programs to the catchall spending bill would give the military much-sought increases for force readiness and the VA additional funding for health care.

But that approach has few fans in the White House, which is seeking money to implement Obama's signature efforts to overhaul financial regulation and the nation's health care system, or the Democratic Senate, where veteran members of the Appropriations Committee want to add a stack of bills covering domestic priorities like homeland security, NASA and federal law enforcement agencies like the FBI.

"You need balance," said Sen. Chuck Schumer, D-N.Y. "We feel as strongly about the domestic side as we do defense."