Jon Kyl, the Republican's second-ranking Senate member, said the party would flex its muscles by stalling the $819 billion stimulus package without a fundamental rethink of the bill's mix of spending and tax cuts.
"I think that we would all agree there will be a 60-vote requirement for the bill. That's the end result of a filibuster," he said on "Fox News Sunday," referring to a parliamentary tactic to drag out debate indefinitely.
To overcome a Republican filibuster, the Democrats would need to amass 60 votes to shut down debate and bring the bill to a vote. Obama's party can now count on 58 votes to the Republicans' 41, with one seat still unresolved.
As the Senate prepared to take up the stimulus bill on Monday, Kyl added: "Our effort is not to delay the bill. We understand the urgency of the situation.
"When I say 'start from scratch,' what I mean is that the basic approach of this bill we believe is wrong."
Republicans, accusing the Democratic majority in Congress of shutting them out of debate, have so far resisted a charm offensive from the new president as he battles to haul the US economy out of recession.
Last Wednesday the House of Representatives approved the gargantuan package without a single Republican vote.
Negotiations were carrying on through the weekend, as Obama invited a bipartisan group of lawmakers to the White House to watch Sunday night's Super Bowl, the climax to the American football season.
"I've talked to some Republicans on the other side of the aisle. We said to them we're open about this. Come to us with your ideas. Let's move forward," Democratic Senator Richard Durbin said on Fox.
Durbin added: "This is not another bill. This is not another political debate.
"We are facing one of the most serious economic crises in our nation's history."