President Trump on Monday pushed for greater price disclosure in health care, signing an executive order that could make thousands of hospitals expose more pricing information and require doctors, health clinics and others to tell patients about out-of-pocket costs upfront.

While President Trump has pledged repeatedly to take on health costs, the signing of the executive order unleashes coordinated efforts from multiple agencies to pursue the goal. It calls for the Department of Health and Human Services to issue a rule within two months that could require hospitals to publicize information on their negotiated rates with insurers for common procedures.

In comments Monday at the White House, Mr. Trump said the order would fundamentally change the health-care marketplace. “There’s frankly no rhyme or reason for what’s been happening for so many years,” he said, adding that the “lack of price transparency has enriched industry giants greatly.”

Industry groups are mobilizing to fight back, saying any requirement that hospitals and insurers disclose negotiated rates would go too far. Lawsuits could be likely, meaning any action could be delayed until after the presidential election. They also said the order lacks many specifics, raising questions about how aggressive the administration will actually be in exposing the murky realm of health-care pricing.

“This effort is all about 2020,” said Tom Nickels, executive vice president of the American Hospital Association, which opposes the plan. “This is their effort to come up with a health-care agenda for 2020.”