WASHINGTON  Top Republicans on Wednesday were hostile toward President Obama’s plan to create a bipartisan commission on cutting projected deficits, raising doubts about the prospects of a main piece of his budget strategy.

Senator Mitch McConnell of Kentucky, the Republican leader in the Senate, was evasive when pressed by reporters at the Capitol. “I’m not going to decide today what we’re going to do in the future,” he said. But the House Republican leader, Representative John A. Boehner of Ohio, seemed to suggest that Republicans might not take their allotted seats on a commission.

“This sounds like political cover for Washington Democrats who are starting to realize that their out-of-control spending is scaring the hell out of the American people,” Mr. Boehner said of the tentative deal between the White House and Congressional Democratic leaders on Tuesday night.

Under that plan, Mr. Obama would establish by executive order an 18-member bipartisan panel to propose how to balance future tax revenue and entitlement program benefits. The group’s recommendations would be due by Dec. 1  after the November elections. Then Congressional leaders would put the package to a vote.