Two key Senate Democrats want to ensure new funding for transportation infrastructure is part of any congressional effort to jump start the economy.

Sen. Frank Lautenberg, D-N.J., and Sen. Daniel P. Moynihan, D-N.Y., Thursday proposed a $7.13 billion three-year supplemental transportation spending bill that would affect highways, mass transit, railroads and aviation.Sen. Lautenberg is chairman of the Senate Appropriations Committee's transportation subcommittee and Sen. Moynihan is chairman of the Senate Environment and Public Works Committee's transportation subcommittee.

The senators said $2.5 billion would go for maintenance and repair of highways and bridges, $1.2 billion for maintenance and improvement of mass transit and $1.4 billion for airport safety and improvement projects. Funds also would be provided for repair and upgrading of the nation's rail systems and to the Coast Guard.

They claimed their proposal could provide funds during the current fiscal year, create 180,000 jobs, adding some $13.5 billion to the gross domestic product.

The two senators acknowledged passage of their measure faces substantial hurdles. Under terms of the 1990 White House-congressional budget agreement, funding for such a proposal would have to be accompanied by corresponding cuts in other programs. On Thursday, the senators did not identify where such cuts might be made.

Sen. Lautenberg suggested that President Bush could declare a budgetary ''emergency" and permit the budget agreement to be violated. The president thus far has opposed a change in the budget agreement.

"We need to make the peace dividend real. We should rebuild our infrastructure on which business and commerce depend," Sen. Lautenberg said.

The two senators also lashed out at the president for praising the recently enacted $151 billion surface transportation bill in Tuesday's State of the Union address and then cutting funding for transportation the following morning in his proposed fiscal 1993 budget.

Sen. Moynihan said the president's budget fell about 8 percent or $1.6 billion short of the funding authorized for highways in the transportation act and about 48 percent or $2.2 billion less than what was authorized for transit spending. Both senators said Congress would act to restore the lost funds.

So far, Sen. Quentin N. Burdick, D-N.D, and Sen. Joseph I. Lieberman, D- Conn., are the only other senators to have endorsed the Moynihan-Lautenberg proposal.