Republicans in the Senate are backing a plan to shave $20 billion from President Barack Obama's budget for the upcoming fiscal year.

The cuts amount to about a 2 percent trim from the $1.13 trillion requested by Obama for agency budgets annually funded by Congress. Senate Budget Committee Democrats have proposed a $4 billion cut.

While small as a percentage of overall spending, the cuts represent an attempt by Republicans to respond to rising voter anger about spending and deficits. And it comes from an unlikely source: the Republicans on the Senate Appropriations Committee, many of whom are viewed with distrust by GOP conservatives as willing accomplices in spending taxpayer dollars and being prone to larding spending bills with pork barrel projects.

The step comes as the powerful Appropriations Committee is getting ready to approve the first of 12 annual spending bills for the budget year beginning in October. The bills are overdue, and it appears increasingly unlikely that many — if any — of them will become law on time.

A letter signed by 12 Republicans on the Appropriations panel says that they won't vote for bills that don't fit within their proposed $1.11 trillion spending cap. That's noteworthy since the panel has a long-standing history of bipartisanship and its GOP members typically provide crucial support to advance the measures past Republican conservatives.

"The American people are saying to us: 'You're spending too much, you're running up too many debts, and we expect you to do something about it,'" said Senate GOP leader Mitch McConnell of Kentucky.

The GOP-proposed cuts are drawn from a bipartisan proposal by Sens. Jeff Sessions, R-Ala., and Claire McCaskill, D-Mo., that has attracted as many as 59 votes in the Senate this year. Democrats supported the cap when voting on the budget last year.

The proposal would still provide for a $10 billion increase over current spending.

Obama has proposed a freeze on most domestic agency budgets, though he exempts homeland security and veterans programs. But he's calling for an $18 billion, 3 percent increase for the Pentagon.

Democrats said the GOP move would cut the increase for defense by more than half and force cuts below current spending for some departments. Republicans didn't propose specific cuts Tuesday, though their votes for the Sessions-McCaskill plan earlier in the year put them on record in favor of such curbs on the Pentagon budget.

The GOP plan, said Appropriations Committee Chairman Daniel Inouye, D-Hawaii, "could result in cutting research funds for traumatic brain injury, worsening the shortage of air traffic controllers, cutting after-school centers and veterans employment programs, to name just a few."

And unlike House GOP lawmakers, Senate Republicans haven't sworn off homestate projects known as earmarks.