LOS ANGELES, Calif.–Mayor Antonio Villaraigosa was part of a chorus, which included President Barack Obama and the U.S. Conference of Mayors, calling on Congress today to pass an extension of the nation’s surface transportation bill or risk putting people out of work.

Without an extension by Sept. 30, officials said, federal funding for highway and bridge repair, mass transit and other projects would be frozen.

They said about 4,000 federal employees would be furloughed, and the government would cease collecting transportation user fees that pay for infrastructure projects.

A 10-day lapse in the transportation bill would cause the government to lose about $1 billion in revenue, Obama said during a speech in the White House Rose Garden.

Congress is currently debating a new transportation bill that would increase federal investment in infrastructure, but it is unlikely to have enough support before the existing bill expires.

In a letter to members of Congress, The Conference of Mayors, which is headed by Villaraigosa, sent a letter to members of Congress, urging passage of the extension without the new investments.

“Key decisions about the scale of future funding commitments and the substance of specific policy reforms should be addressed in the successor legislation,” the letter says. “Today there is growing anxiety that for the first time in decades, Congress could fail to fund our national transportation system.”

A lapse in the bill could do “irreperable harm to our already crumbling infrastructure,” the letter states.

Villaraigosa has actively lobbied for an expanded transportation bill, making at least seven trips to Washington, D.C., to advocate for a federal loan program. The so-called America Fast Forward plan would provide loans and loan guarantees to cities that demonstrate local investment in transportation infrastructure.

Villaraigosa argues the program could create one million jobs nationwide.

“We need Congress to create jobs,” he said, “but we will first ask that they honor that great Hippocratic oath and ‘first, do no harm.”‘

Officials pointed to Congress’ failure to pass an extension of a bill that funds aviation safety and airport improvements. A lapse in the bill that funds the Federal Aviation Administration furloughed about 4,000 employees for more than a week.

“This Labor Day, let’s not only acknowledge the close of summer, but let’s also end this ‘silly season’ in Washington, D.C.,” Villaraigosa said.

“It’s time for Congress to move with purpose on the one issue most Americans will be pondering this Labor Day–how to keep or find a good job.”