JUDY WOODRUFF: From the president today, the first salvo against his predecessor's climate agenda. Instead, he's launched an aggressive campaign he says will help the coal, oil and gas industries.

John Yang begins our coverage.

JOHN YANG: With coal miners looking on at EPA headquarters, President Trump took action to undo most of President Obama's climate change legacy.

PRESIDENT DONALD TRUMP: Perhaps no single regulation threatens our miners, energy workers and companies more than this crushing attack on American industry.

JOHN YANG: He signed an executive order targeting more than a half-dozen major regulations. The biggest target? The Clean Power Plan to restrict greenhouse gas emissions at coal-fired power plants, the centerpiece of Obama's global warming policies.

FORMER PRESIDENT BARACK OBAMA: The idea of setting standards and cutting carbon pollution is not new. It's not radical. What is new is that, starting today, Washington is starting to catch up with the vision of the rest of the country.

JOHN YANG: It's been on hold while coal states and the energy industry challenged it in court as an unconstitutional power grab.

Today's order mandates a review of the Clean Power Plan, lifts a moratorium on new coal leases on federal lands, starts a review of reducing methane emissions in oil and natural gas production, and launches an assessment of rules governing hydraulic fracturing, also called fracking, by oil and gas drillers.

During the campaign, Mr. Trump slammed the Obama administration for waging a war on coal and vowed to bring back mining jobs.

PRESIDENT DONALD TRUMP: Today, I'm taking bold action to follow through on that promise. My administration is putting an end to the war on coal. We're going to have clean coal, really clean coal.

JOHN YANG: But coal mines have been losing jobs for many years because of a range of factors, including automation and competition from cheap natural gas.

Environmentalists warned that the president's action raise questions about whether the United States can meet the obligations under the 2015 Paris climate agreement.

In a statement, the head of the Sierra Club said: "President Trump's sweeping order is the single biggest attack on climate action in U.S. history, period." The group vowed an all-out fight.

For the PBS NewsHour, I'm John Yang.