President Barack Obama's relationship with environmentalists sits on thin ice after a major league meltdown over whether he will really defend their biggest demand: EPA climate change rules.

Tensions have crossed into the danger zone between the two camps after a year of cross-ups, including the failure to get a cap-and-trade bill through the Senate and Obama’s embrace of what historically have been green no-no’s like oil drilling and nuclear power.

Angst grew this week after Obama failed to use a major energy policy speech at Georgetown University to explicitly back the EPA's global warming agenda. Then, in what might have begun as a misunderstanding over acronyms, the AP reported that the president was leaning on House Democrats to accept a GOP-authored budget rider that would thwart EPA's greenhouse gas regulations.

The White House furiously denied the story, but the fate of the budget debate over the next eight days could govern the relationship between the administration and environmental community through the 2012 election.

"It's clear the president is running for reelection and that at this point, environmental protection is not on his top list of priorities," said Frank O'Donnell, president of Clean Air Watch.

“I think everyone in the environmental conservation community, if they’re honest, is frustrated,” said Rodger Schlickeisen, president of the Defenders of Wildlife.

“If they hesitate to say so, it’s because we’re grateful it’s so much better than the last administration and it’s so much better than something else that could occur,” he added. “But I think anybody in the environmental conservation community would be dishonest if we didn’t hope for and expect more than we’ve seen. And that’s pretty much across the board.”

Obama officials insist they've been doing the environmentalists right, starting with a record federal investment of tens of billions of dollars for clean energy technologies.

On Wednesday, Obama talked up a number of other regulatory tools he has in hand to overhaul energy policy, including new fuel-economy standards aimed at helping reduce foreign oil imports by a third over the next decade. On Friday, he plugged the National Clean Fleets Partnership, a public-private program that encourages companies to incorporate alternative fuels, plug-in cars and trucks and fuel-saving measures into their daily operations. Next week, Obama will visit a wind-energy turbine shop outside Philadelphia.

And when it comes to the climate rules, the EPA says the president has the agency's back. "The administration has been clear in its support of EPA's authority to develop reasonable, common-sense standards to address unchecked carbon pollution," said EPA spokesman Brendan Gilfillan.

But the environmentalists still need more convincing. Words and actions matter, and Obama on more than one occasion has left them wanting to hear and see more — a lot more.

In response to the GOP gains in Congress, greens overhauled their own budget and lobbying strategy to make defending the pending EPA rules their top priority. Those climate rules are under attack from riders in the House’s spending bill passed in February, a stand-alone bill on the House floor and various Senate amendments to small-business legislation.

The House and Senate votes are expected next week, and the federal government runs out of money on April 8, so things are coming to a head.

Environmentalists have heard Obama officials say he'd veto any bill that on its own restricts EPA's authority. They say they haven’t gotten a public statement from the president on what he would do if the language was folded into a larger, must-pass item, like the six-month appropriations measure being negotiated on Capitol Hill.

Hence their angst after the AP story appeared Wednesday, making it appear that a cave-in on EPA was in the works.

The greens burned up the phone lines to their administration contacts demanding answers, and Senate Democratic leaders fired off statements vowing to defend EPA. The White House tried desperately to put out the fire, insisting the story was incorrect and ultimately issued a statement pledging to oppose environmental riders — but did not issue a specific veto threat.

“It’s great they have reaffirmed their opposition to anti-environmental riders,” said Gene Karpinski, president of the League of Conservation Voters. “That needs to remain a clear line in the sand.”

Even though the stopgap spending bill is temporary, greens cite the never-die nature of former President George W. Bush's tax cuts and restrictions during the 1990s over developing new fuel-economy standards as the reason they fear more trouble down the road.

"We're all aware anything that's given away now could be pretty close to a permanent giveaway, however it's couched," said O’Donnell, of Clean Air Watch. "The problem I see is that if you keep making concessions, it doesn't seem to satisfy the opponents. It merely whets the appetite for more blood."

With the current budget showdown, Obama isn't just being asked to back the EPA climate regulations. Riders dealing with toxic air pollution, mountaintop mining, endangered species protections, global warming program funding and the Chesapeake Bay area also in the mix.

History is a factor as well. Last year, Obama didn't give the push for cap-and-trade legislation environmentalists had banked on, as the White House seemingly prioritized other issues like health care. Now, greens are competing for oxygen with groups concerned about other liberal causes, like Planned Parenthood and NPR.

Also hurting efforts is last month’s departure of Carol Browner — a former EPA chief and trusted go-to person for greens — as the White House energy and climate adviser. Heather Zichal, Browner’s longtime deputy, now has the portfolio from inside the Domestic Policy Council.

"It's a little different than having a separate power base," O'Donnell said. "In the world of bureaucracy, it's a downgrade."

Alas, the greens don't have many other places to go. House Democrats are back in the minority wilderness, and some Senate Democrats are searching for ways to kneecap EPA’s climate policy, too.

Environmentalists don't need to be reminded that they battled George W. Bush for eight years running. But even as they notch victories under Obama on mercury limits for power plants, EPA enforcement actions and renewable energy budgets — items they fought for during the last administration that also equal cuts in greenhouse gas emissions — several said they are not satisfied to be thrown under the bus on an EPA climate change agenda that they successfully fought all the way to the Supreme Court.

"That's pretty lame," said Matt Pawa, a Boston-based attorney behind a major global warming lawsuit against power companies. "It's like saying, 'We'll give you jobs but we won't give you the right to vote.' It's a backdoor way of trying to do something that demands overriding urgency, front-door urgency, action now, action that's been promised."

Just days before Obama's party got hammered in last November's midterms, the president told Rolling Stone magazine that it would be "just irresponsible" for his base to sit out the election, saying it would hamper progress on issues like climate change. As Al Gore remembers from the 2000 election, however, greens could certainly make a Democrat’s life more difficult if they sit on the sidelines.

Defenders of Wildlife’s Schlickeisen said it’s too early to make threats.

"We've earned the right to be critical, but I'm not that critical,” he said. “I'm in the camp of still reminding them they've got promises they've made of protecting the environment, and they've still got time to do it."

Browner told POLITICO on Thursday that she's not concerned about where the White House falls on her former portfolio.

"I think the president and the administration have a very strong record of supporting strong energy policies, strong environmental policies," she said. "And I don't think anything is going to change in that regard."