Speaker Nancy Pelosi (D-Calif.) threw her weight Thursday behind a massive transportation bill but threw cold water on the potential for another stimulus package any time soon.“I am a proponent for bringing up a full transportation bill, which is a great jobs bill, [and] at some point we may need to do an extension of unemployment benefits,— Pelosi said. But she said she didn’t yet see the need for a massive new stimulus package.“We have to be very careful about spending on this,— she said.Other Democrats, including House Transportation and Infrastructure Chairman James Oberstar (D-Minn.) and Rep. Peter DeFazio (D-Ore.), who heads a Transportation subcommittee, have long supported a much larger stimulus package for infrastructure.And House Rules Chairwoman Louise Slaughter (D-N.Y.) said Thursday that she and many other Democrats wanted the infrastructure package to be much larger in the original stimulus bill but that it was pared down in a failed effort to gain Republican votes. Slaughter also said Congress would act if the economy continues to stumble.“We’re not just going to sit here,— she said.Oberstar has proposed a $500 billion, six-year transportation measure, but Democrats have not yet agreed on a way to fully pay for it. The Obama administration has proposed delaying action on a long-term bill until 2011 and wants a stop-gap measure passed this month to prevent the transportation fund from running out sometime in August or September.Oberstar and DeFazio said Wednesday that they would be willing to support a short-term funding plan this month but are adamantly opposed to an 18-month extension.