Environmentalists are promising a battle royale next month as the titans of industry clash with the Obama administration and its activist supporters in the biggest legal battle over climate change to date.

"Just weeks from now, NRDC and its allies will be fighting in the D.C. Circuit Court to defend the Clean Power Plan in one of the most important courtroom battles ever for our climate," said Rhea Suh, president of the Natural Resources Defense Council, in a Friday message to donors.

"NRDC's legal team is gearing up for our full-scale defense of the Clean Power Plan in court, but we can't win against such powerful foes without your immediate help," Suh added, playing up the fight to drum up donations.

"We'll be up against powerful coal industry giants, like Peabody Energy — America's largest coal company — that are determined to kill President Obama's historic plan to tackle climate change," she added. "If they win, it will slam the door on our clean energy future."

Suh has been sending similar messages all week, pitting environmental groups and the Environmental Protection Agency against the goliaths of the coal industry such as Peabody, Murray Energy, Southern Co., the National Mining Association, the North American Coal Corp. and the American Coalition for Clean Coal Electricity.

Suh said the fossil fuel groups are "all working to stymie our climate progress and keep us shackled to fossil fuels." Just a few days ago, NRDC started circulating a petition to get coal companies to withdraw their legal challenges against the administration. But that isn't likely.

Thirty states and a number of industry groups, unions and others, along with the coal companies, are suing the EPA over the Clean Power Plan, arguing that it violates the law.

Opponents of the Clean Power Plan were successful in petitioning the Supreme Court to halt the climate plan while the lawsuit plays out in the D.C. federal appeals court. Oral arguments are slated for June 2.

"The Supreme Court has temporarily halted the Clean Power Plan — but Big Coal will be pushing hard to dismantle it entirely on June 2 when its legal merits are debated for the first time in federal court," Suh said.