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WASHINGTON -- With GOP resistance mounting, President Obama urged lawmakers from both parties Friday to back his stimulus package, saying the economy's dire problems require congressional action.

"I recognize that there are still some differences around the table and between the administration and members of Congress about particular details of the plan," Obama said as he sat down with the House and Senate leaders from both parties in the White House's Roosevelt Room.

"But what I think unifies the group is recognition that we are experiencing an unprecedented, perhaps, economic crisis that has to be dealt with rapidly," he said.

Many Republican lawmakers say the $825 billion package is too costly, and that too much of the spending is for long-range projects that won't aid the economy quickly. Some economists say the package should be even bigger, however, and it was unclear whether Republicans would have much impact.

House and Senate GOP leaders "had some constructive suggestions, which we'll review," House Speaker Nancy Pelosi, D-Calif., told reporters after the meeting.

Speaking at the National Press Club shortly after the White House gathering, Sen. Mitch McConnell of Kentucky, the Republican leader in the Senate, said he believes the measure will clear Congress by the mid-February target date set by Obama and Democratic leaders.

House Republican Leader John Boehner said he and his colleagues told Obama they feel the stimulus package is too expensive and too slow. He said Republicans told Obama of their own plans to "get fast-acting tax relief in the hands of American families and small businesses, because at the end of the day, government can't solve this problem."

Republicans have been seeking deeper tax cuts and have said there was no reliable estimate of the bill's impact on employment.

Democrats tried to mitigate the impact of a Congressional Budget Office study that questioned administration claims that the money could be spent fast enough to reduce joblessness quickly.

Senate Majority Leader Harry Reid, D-Nev., said there was "significant discussion about the CBO numbers."

He said Obama's budget director, Peter Orszag, who recently headed the CBO, told participants that the study analyzed only 40 percent of the pending stimulus bill and that Orszag "would guarantee that at least 75 percent of the bill would go directly into the economy within the first 18 months."

Senate Finance Committee Chairman Max Baucus on Friday released a Senate version of the tax-cutting portion of the bill. The legislation could have a more bipartisan look in the Senate, where it takes 60 votes out of 100 to overcome procedural blocks.

Baucus' $355 billion proposal would offer a bonus payment of $300 to senior citizens receiving Social Security and veterans who get disability payments.

The plan also includes a $500 tax cut for most workers, help to pay for college, tax cuts for businesses and to promote renewable energy, and $87 billion to help states struggling with their budgets for the Medicaid health care program for the poor and disabled.

Baucus's committee will vote on the plan next week.

The House Ways and Means Committee on Thursday approved $275 billion in tax cuts on a party-line vote of 24-13. The House Energy and Commerce Committee, also working on the bill, cleared $2.8 billion to expand broadband communications service. And on Wednesday night, the House Appropriations Committee approved a $358 billion spending measure on a 35-22 party-line vote.

FOX News' Major Garrett and the Associated Press contributed to this report.