WASHINGTON — The fate of $600 to $1,200 rebate checks for more than 100 million Americans is in limbo after Senate Republicans blocked a bid by Democrats to add $44 billion in help for the elderly, disabled veterans, the unemployed and businesses to the House-passed economic aid package.

GOP senators banded together yesterday to thwart the $205 billion plan, leaving Democrats with a difficult choice either to quickly accept a House bill they have said is inadequate or risk being blamed for delaying a measure designed as a swift shot in the arm for the lagging economy.

The tally was 58-41 to end debate on the Senate measure, just short of the 60 votes Democrats would have needed to scale procedural hurdles and move the bill to a final vote. Hawai'i Sens. Daniel Akaka and Daniel K. Inouye, both Democrats, voted for the measure.

In a suspenseful showdown vote that capped days of partisan infighting and procedural jockeying, eight Republicans — four of them up for re-election this year — joined Democrats to back the plan, bucking GOP leaders and President Bush, who objected to the costly add-ons.

Democrats choreographed the vote for maximum political advantage, presenting their aid proposal as a take-it-or-leave-it proposition for Republicans and calling back their presidential candidates to make a show of party unity behind their stimulus plan. They calculated that Republicans would pay a steep price for opposing rebates for older Americans and disabled veterans, as well as heating aid for the poor, unemployment benefits and a much larger collection of business tax breaks than the House approved.

Even after their effort fell short yesterday, Democrats seemed determined to keep the pressure on Republicans to accept the measure, threatening to hold more votes on it in the coming days.

Majority Leader Harry Reid, D-Nev., is "going to give Republicans a chance to reconsider their vote against efforts to strengthen the economy by helping those who need it most," his spokesman, Jim Manley, said last night.

Republicans said they were ready to accept rebates for seniors and disabled veterans and accused Democrats of delaying the stimulus plan for political gain and loading it down with special-interest extras.

"Our constituents will look at us as the folks that slowed it down (and) added a bunch of spending to it," said Sen. Jon Kyl of Arizona, the Republican whip, who called the measure "a Christmas tree package."