President Donald Trump on Monday said he would focus this week on pushing for U.S. infrastructure projects to rebuild or modernize the nation’s roads, bridges, dams and broadband lines. He had pledged during his presidential campaign to spend $1 trillion on public works projects.

A key question remains unanswered, according to The Wall Street Journal: How will Trump get private investors to put up most of the money for these projects?

“There has so far been little detail on Mr. Trump’s lofty infrastructure promise,” the newspaper reported. “Trump’s advisers say they can get private investors to put up the capital for such projects by curtailing permitting requirements and regulations, and by offering incentives to states and cities to turn to the private sector for financing.”

The president on Monday described a plan to privatize the U.S. air-traffic control system to improve safety and modernize a vital part of the country’s