"It is important that Congress act ... and it's important to make sure that taxpayers' money be paid back if any is given to the companies," he said.
Democrats want the White House to use part of the already approved $700bn bailout of the finance industry to rescue the car makers.
But the Bush administration has insisted the money should come from a $25bn stream of loans designed to help the manufacturers produce more fuel-efficient vehicles.
Barney Frank, the House of Representatives Financial Services Committee chairman, said inaction on a bailout "would be a disaster," following Friday's announcement of the worst US unemployment figures for 34 years.
"For us to do nothing, to allow bankruptcies and failures in one or three of these companies in the midst of the worst credit crisis and the worst unemployment situation that we've had in 70 years, would be a disaster,'' Frank said.
Spencer Bachus, the committee's top Republican, said he could possibly support granting the industry emergency bailout loans, but with caveats.
"The only course I could possibly endorse would be limited transitional assistance to allow the American domestic automobile industry to return to solvency and profitability," he said.
GM has asked Congress for $18bn, including $4bn by the end of December to avoid collapse, while Chrysler sought $7bn, also by the end of the month.
Ford said it was seeking $9bn in credit as insurance against any potential difficulties.
The three executives travelled by car for their congressional appearance this week, two weeks after a botched bid for aid that included criticism for flying to Washington in private jets.