Elaine Chao testifies during her confirmation hearing to be the next transportation secretary. (Chip Somodevilla/Getty Images)

The Senate Committee on Commerce, Science and Transportation voted unanimously to approve Elaine Chao’s nomination as transportation secretary Tuesday, pushing the former labor secretary and Washington insider closer to a new official role shaping one of President Trump’s signature initiatives.

Chao’s nomination will now move to the full Senate, but a hearing has not yet been scheduled.

Trump pledged a big infrastructure boost during his campaign, and Chao’s supporters say that she is well positioned to help turn those promises into reality.

But key issues — including how much would be spent on what, and how it would be paid for — remain uncertain. Trump talked of a $1 trillion effort, which his advisers said would include a rush of private investment lured by tax breaks, although economists have questioned those assumptions.

Following Trump’s inauguration, the White House website posted an idea for a major source of transportation funding, although it did not detail how the windfall would materialize. The president’s team promised to eliminate “harmful and unnecessary” climate and other environmental regulations and to tap vast domestic energy reserves to rebuild roads and infrastructure.

“We must take advantage of the estimated $50 trillion in untapped shale, oil, and natural gas reserves, especially those on federal lands that the American people own,” according to the site. “We will use the revenues from energy production to rebuild our roads, schools, bridges and public infrastructure,” it said.

Chao, the wife of Senate Majority Leader Mitch McConnell (R-Ky.), did not raise the notion of tying energy production to transportation funding in her genial confirmation hearing, where she received a warm welcome and a host of requests from senators to visit their states — and fund their hometown projects.

Democrats were offering their own $1 trillion infrastructure plan Tuesday, but said their package would rely on direct federal spending, and also cover schools, broadband and veterans hospitals.

Chao’s public tone and emphasis on the scope of potential new investments has shifted some since her nomination.

In responding to a Senate questionnaire, Chao noted that “with or without a new infusion of funds,” much work is needed to improve how infrastructure gets built in the United States.

But just ahead of her Jan. 11 confirmation hearing, Chao and her transition advisers added that given “the President-Elect’s focus on executing a major infrastructure initiative,” Chao is the right person to “help forge the collaboration needed between the executive branch, the legislative branch and numerous stakeholders to make these key initiatives a reality.”

Sen. Cory Booker (D-N.J.) pressed Chao at the hearing to see if administration plans went beyond the $137 billion in tax incentives Trump advisers described, saying Trump’s chief strategist, Stephen K. Bannon, has called for new direct investments in infrastructure to ensure the nation’s competitiveness internationally.

“Do you and President-elect Trump support an infrastructure package that will include direct federal spending?” Booker asked.

“I believe the answer is yes,” Chao replied.