Environmentalists are gearing up to battle President-elect Donald Trump, who promised on the campaign trail to roll back laws and regulations that protect the environment and fight global warming.

Trump also said he would withdraw the United States, the world's second-largest greenhouse-gas polluter after China, from the Paris global climate accord signed in 2015 by 192 countries.

But the Republican real-estate tycoon has modified that position since his November 8 election win.

In a recent interview with The New York Times, Trump hinted he may support global accords on climate change, saying he had "an open mind."

As a candidate Trump had called the concept of global warming a hoax, but he acknowledged to the Times there was "some connectivity" between human activity and climate change.

"Some, something. It depends on how much," he said, adding that he would still remain concerned about how much green measures would "cost our companies."

On Monday, Trump held a lengthy meeting in New York with Democratic former vice president Al Gore, a key environmentalist and leader in the fight against global warming.

"I found it an extremely interesting conversation and to be continued, and I'm just going to leave it at that," Gore told reporters after his talk with Trump.

- Bracing for Trump -

Environmentalists are bracing for Trump to take office on January 20 with his Republican Party in control of Congress.

"If Trump tries to go backwards on climate change and the protection of the environment, he will run headlong into an organized mass of people who will fight him in the courts, in Congress and on the streets," vowed Michael Brune, executive director of the Sierra Club, one of the largest US environmental organizations, with 2.4 million members.

"We got more new members joining the Sierra Club in three weeks since the election than for the full year... with 9,000 new monthly donors," Brune said in an interview. "People are worried and feel angry."

Environmentalists criticize the president-elect's choices for interviewees as he prepares his transition to the presidency, talking to billionaires linked to the oil and coal industries and notorious climate-change skeptics.

One of them, Scott Pruitt, the Oklahoma attorney general who is suing the Environmental Protection Agency, is reportedly Trump's pick to head the EPA -- which Obama used via executive order to cut carbon emissions.

The EPA would be the vehicle Trump could use to roll back Obama's regulations.

In addition, the chief executive of oil and gas giant ExxonMobil, Rex Tillerson, has emerged as a candidate to be secretary of state, the nation's top diplomat.

The mobilization of environmentalists against Trump has taken to television, for example, with John Oliver, the British host of "Last Week Tonight," a weekly HBO show, calling for action.

Oliver recently asked Americans to donate to and join environmental protection organizations, citing in particular the Natural Resources Defense Council (NRDC).

- 'Outpouring of support' -

In an interview, Susan Casey-Lefkowitz, chief program officer of the NRDC, a New York-based organization with 2.5 million members, said that since Trump's election there has been "a real outpouring of support -- people standing with us against any potential rollback from environmental protection."

She said NRDC is preparing a petition "that will go to Trump immediately to let him know that people do not want rollback from core environmental protection."

A key tactic would be to focus on the importance of protecting air and water quality, two goals widely shared, even by Trump's supporters, she said.

For May Boeve, the head of climate campaign group 350.org, the best way to mobilize working-class Americans who voted for Trump "is to push for a 100 percent renewable-energy economy that works for all."

"Clean energy remains the greatest potential job creator in the 21st century, while climate change is still our greatest threat," Boeve said.

The New York-based nonprofit organization is "preparing for the fight of our lives," she said, and planning a mass demonstration in Washington when Trump is in the White House.

Taking a more wait-and-see stance was Elliot Diringer, an expert at the Center for Climate and Energy Solutions, a bipartisan nonprofit organization that works to reconcile energy production and climate protection.

"One of the biggest lessons of the election season was unpredictability and it remains true today," he said.

"So we cannot prejudge and hopefully he will listen to scientists and business leaders and others and take climate seriously," Diringer added.