Transportation Secretary Elaine Chao on Wednesday endorsed a congressional push to invest in the nation’s infrastructure in remarks before a gathering of state transportation officials.

“We need to address these challenges because our nation’s prosperity, public safety and our public infrastructure have never been more intertwined,” Chao said, underscoring that “how to pay for” infrastructure needs would have to be resolved.

Her speech to the American Association of State Highway and Transportation Officials (AASHTO) was preceded by Republican and Democratic leaders of the two principal House and Senate committees., who vowed to provide bipartisan support for the effort.

Chao said the four congressional leaders who be “drivers of the infrastructure package.”

“I look forward to working with them,” she said. “As the president noted in his State of the Union address, infrastructure is the backbone of the nation’s economy.”

After a 2016 presidential campaign in which both candidates addressed the need for infrastructure improvements, the issue faltered over how to fund the effort, and that question persists as the American Society of Civil Engineers (ASCE) estimated two years ago that almost $4.6 trillion was required to bring all systems up to an acceptable standard.

“Infrastructure is among the two or three big policy matters upon which leaders from both parties can agree,” Chao told AASHTO’s annual convention.

She cited expenditures of $63 billion in investment in infrastructure since she assumed the job.

“We are streamlining the permitting and approval process so that infrastructure projects can be delivered more quickly, while continuing to protect the environment and protect safety standards,” Chao said.

Before her luncheon speech, the assembled transportation officials heard from Sen. John Barrasso (R-Wyo.), chairman of the Senate’s Environment and Public Works Committee; Sen. Thomas R. Carper (D-Del.), ranking member on the Senate committee; Rep. Peter A. DeFazio, chairman of the House Transportation and Infrastructure Committee; and Rep. Sam Graves (R-Mo.), ranking member on the House committee.

“Surface transportation infrastructure connects all of us,” Barrasso said. “The time has come to make significant investment in our roads and bridges, and keep the Highway Trust Fund solvent.”

The funding process is complicated, but it can be summarized by saying the primary source of the Highway Trust Fund are the federal tax on gas and diesel fuel. Gas tax revenue has declined for a variety of reasons, among them greater fuel efficiency and hybrid or electric cars.

“Over the last several years there have been a lot of promises made over funding infrastructure,” Carper said. “We start off every session of Congress saying ‘we’re going to do infrastructure’ and we’re not very good at keeping that promise.

Nevertheless, he said, the Senate committee is “pretty good at working with each other across the aisle. I think there’s reason for hope.”

Said DeFazio: “The costs of doing nothing are absolutely astronomical.”

He again raised the prospect of increasing the federal gas tax, which has remained at 18.4 cents since 1993, as a short-term means of boosting the trust fund while a vehicle-miles-traveled tax can be put into place.

“There’s a point at which the American people get it,” DeFazio said. “They’re tired of congestion, they’re tired of blowing out tires in potholes and they’re tired of transit systems that are decrepit and don’t work.”

Graves told the group there was ample support from Congress for an infrastructure package.

“The Senate wants to do something. The House wants to do something. Democrats, Republicans, the President, everybody wants to get something done,” Graves said. “If we don’t have something out of the House by August I don’t think it’s going to happen, simply because the election and everything that comes along with that.”