President Barack Obama's proposal is similar to the presidential line-item veto authority that was struck down by the Supreme Court in the late 1990s.
Other senior Democrats have yet to support the White House proposal, sent to Congress on Monday. Speaker Nancy Pelosi (Calif.) and Senate Majority Leader Harry Reid (Nev.) have said they would review the proposal. Democrats backing the plan are Sen. Russ Feingold (D-Wis.) and House Blue Dogs, who have made similar proposals, as well as House Budget Chairman John Spratt (D-S.C.), who will introduce Obama's proposal in the House.
House Republicans said they "welcomed" Obama's proposal but said it wasn't nearly enough to deal with the $13 trillion debt.
Slaughter warned that the new presidential authority could weaken Congress's power of the purse, echoing the concerns of appropriators, most notably Sen. Robert Byrd (D-W.Va.).
"I do not believe that it's wise for Congress to hand over its Constitutionally-mandated responsibilities in any situation, but especially not when it comes to appropriations," Slaughter said. "This Congress — joined by the current Administration — has worked very hard to bring down the deficit and restore fiscal discipline and I am not sure that giving up our authority over this is the best way to lead."