WASHINGTON — Congressional leaders moved quickly into intense negotiations with the Obama administration on Tuesday after the Senate voted to approve an $838 billion economic stimulus plan, and officials said the talks were on a fast track to finish the legislation perhaps by the end of this week.

In a sign of their determination to reconcile the differences between the Senate bill and the $820 billion House version swiftly, the White House chief of staff, Rahm Emanuel, and the budget director, Peter R. Orszag, huddled at the Capitol on Tuesday evening with Speaker Nancy Pelosi; the Senate majority leader, Harry Reid of Nevada; and other lawmakers.

Participants in the talks said they wanted to reduce the overall price to just under $800 billion.

The officials worked late into the night, with Mr. Reid shuttling between meetings with senators in his office and House leaders in Ms. Pelosi’s suite. Centrist senators who were crucial to the stimulus deal, Susan Collins and Olympia J. Snowe, Republicans of Maine, Ben Nelson, Democrat of Nebraska, and Joseph I. Lieberman, independent of Connecticut, returned around 9 p.m. for the talks and left about an hour later.

The group broke for the night shortly before 11:30 p.m. “We’re not there,” Mr. Reid said. “But we have made a significant amount of progress in the last 10 hours.”

Despite the tight timetable, Mr. Emanuel said, the bill could still be finalized this week. “You are in the legislative branch,” he said. “Anything is possible.” He added, “Everybody knows the seriousness of the economic crisis.”

Even before the Senate voted 61 to 37 to approve the stimulus bill, President Obama met with Ms. Pelosi and Mr. Reid at the White House on Tuesday morning. The president then traveled to Fort Myers, Fla., to showcase a prominent Republican supporter of the plan, Gov. Charlie Crist.

Among the differences to be resolved were proposals in the House bill to subsidize private health coverage for the unemployed and to offer temporary Medicaid coverage for those who cannot retain private insurance. The Senate bill provides $10 billion less in subsidies and does not offer expanded Medicaid. The Senate cuts were likely to be part of the final bill.

Over all, the bills reflect differences of tens of billions of dollars in spending priorities.

Mr. Obama announced the Senate’s passage of the bill in the middle of a question-and-answer session with voters in Fort Myers. He did not mention that it passed with only three Republican votes.

“We’ve got a little more work to do over the next couple of days,” Mr. Obama said, perhaps understating the task ahead. “But it’s a good start.”

Administration officials said that one priority would be to restore Mr. Obama’s middle-class tax cut to its original size. The Senate, trying to lower the cost of the plan, had trimmed it by more than $2 billion.

Congressional leaders have said they want the bill on Mr. Obama’s desk by Monday, and Ms. Pelosi has said Congress would not recess next week unless the bill was done.

The president told the audience that his political future depended on the economy’s rebounding. “I’m not going to make any excuses,” he said. “If stuff hasn’t worked and people don’t feel like I’ve led the country in the right direction, then you’ll have a new president.”

The unemployment rate in Fort Myers was 10 percent in December, more than triple the rate of two years ago. In the last year, about 12,000 jobs have been lost in the Lee County area, a small slice of the 255,000 jobs lost across the state.

Appearing with Mr. Obama was Governor Crist, who last year was mentioned as a contender to be Senator John McCain’s running mate. Mr. Crist has sided with Mr. Obama, rather than with Mr. McCain, who has been one of the plan’s biggest critics in the Senate.

“This issue of helping our country is about helping our country,” Mr. Crist said. “This is not about partisan politics. This is about rising above that, helping America, and reigniting our economy.”