Shortly after launching, the $1 billion Cash for Clunkers program may be almost spent out. Administration weighs next step.

NEW YORK (CNNMoney.com) -- This much seems certain about the Cash for Clunkers program: Consumers are happy to take government rebates to buy new cars.

The fate of the $1 billion trade-in program was up in the air over concerns that it may have already burned through its funds less than a week after it was officially launched.

It was unclear whether car buyers would be able Friday to trade in clunkers.

Congressional sources said early Thursday evening that the program would be put on hold. But Obama administration officials said later that Clunkers had not been suspended and that they were studying the situation.

"Auto dealers and consumers should have confidence that all valid ... transactions that have taken place to date will be honored," a White House official said in a statement.

An official at the Department of Transportation, which manages Cash for Clunkers, said the administration would try to work with Congress to find more funds to keep it going.

One of the program's main champions in Congress, Sen. Debbie Stabenow, D-Mich., called on Congress to appropriate more money.

Stabenow said the effort has provided an important boost to the economy and resulted in 200,000 car sales.

"I am delighted to hear dealers say that all of their salespeople are busy and they are selling more cars in a day than they had been selling in a month," Stabenow said.

Meanwhile, the Transportation Department was sorting out how much of the plan's funds have already been committed.

Cash for Clunkers, which Congress passed in June, is set to end on Nov. 1 or whenever its $1 billion budget has been depleted.

An early version of the Clunkers proposal in Congress called for appropriating $4 billion.

Under the plan as enacted, vehicles purchased after July 1 will be eligible for refund vouchers worth $3,500 to $4,500 on traded-in gas guzzlers. The trade-in vehicle has to get combined city and highway fuel economy ratings of 18 miles per gallon or less
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via CNNMoney.com (by Jennifer Liberto and Peter Valdes-Dapena, CNNMoney.com senior writers)