President Obama has made environmental safeguards one of the selling points of the Trans-Pacific Partnership. But environmental groups aren’t buying.

The influential environmental groups — a key part of the effort to rally the Democratic base against the fast-track bill for trade talks — believe that a new trade pact could set back important gains achieved over the past two decades. By contrast, the White House argues, as senior adviser Brian Deese put it in a recent Web posting, that this is “a once-in-a-generation chance to protect our oceans, wildlife, and the environment.”

The trade issue pits Obama, who has devoted himself to slowing climate change, against environmental groups, which are clamoring for tougher terms. In a largely unpublicized May 21 meeting with the heads of a handful of major environmental groups including the Sierra Club, the Natural Resources Defense Council and the League of Conservation Voters, Obama asked for their trust and help persuading members of Congress to give him fast-track authority to conclude the TPP agreement.

But environmental groups, his natural allies in many ways, are still not willing to grant Obama that trust. And the president seemed more focused on explaining his position than hearing theirs, according to someone familiar with the meeting.

“The president can’t just come into office and say ‘trust me,’ because we have a couple of decades of experience where these trade agreements have been used to undermine environmental laws in other countries,” said Friends of the Earth president Erich Pica, who was not at the meeting. “So there’s a higher bar than just ‘trust us’ on trade.”

Rarely has the president been so isolated from virtually all his traditional Democratic constituencies. But this is not the first time gaps have opened up between Obama and environmental groups. Close cooperation between the White House and the environmental advocacy community on issues such as clean air regulations affecting coal plants and higher fuel efficiency standards for vehicles has not stopped environmental leaders from marching on the White House over the Keystone XL pipeline or filing lawsuits for tougher regulatory enforcement.

Environmental groups are still noisily demanding that the president block Royal Dutch Shell plans to drill in Alaska’s Arctic, impose tougher regulation of oil and gas fracking, limit liquefied natural gas exports and reject the Keystone XL application.

Their greatest fear about the trade pact under negotiation is that it would allow multinational corporations to ask international tribunals to overrule domestic regulations and laws. Rather than raise environmental standards to higher levels, the agreement would result in a “race to the bottom,” according to League of Conservation Voters president Gene Karpinski.

“Many provisions under negotiation in pending trade deals could undermine important progress on top environmental concerns,” Karpinski said in a statement last week.

The two prominent environmental groups have been supportive of Obama’s positions in trade talks but have not yet formally endorsed the outcome. Oceana and the World Wildlife Fund like TPP provisions that the administration says would protect ocean life, forests and endangered species. Unlike 43 other environmental groups, they did not sign a June 11 letter to members of Congress opposing fast-track authority for the president.

“Harmful fisheries subsidies promote overfishing, pushing fleets to fish longer, harder and farther away than would otherwise be economically possible,” Dustin Cranor, communications director for Oceana, said in an e-mail. “The TPP countries produce one-third of the world’s wild seafood by weight and a TPP deal on fisheries subsidies could result in a big win for the oceans.”

These groups have come under pressure from their environmental colleagues to remain neutral and refrain from endorsing fast-track authority for the president, which is the most immediate legislative issue

And environmental groups have good relationships with many West Coast Democrats, who appreciate the benefits of free trade but also count themselves strong environmental advocates.

Those who voted for fast-track authority included Reps. Sam Farr (D-Calif.) and Scott Peters (D-Calif.). The director of the Sierra Club’s Responsible Trade Program, Ilana Solomon, called both “environmental champions” and said that “we’ve been urging them and other members who have been strong on environment and the climate that they can’t have it both ways.”

But Farr on his Web site said that whereas past trade deals made the environment part of sidebar agreements, the new trade deal would make them “statutory law.” And if those standards aren’t adequate, he said, he reserves the right to vote against the final agreement. For now, he said, he thinks that fast track is the best way forward with negotiations and that a deal could benefit the Central Coast region he represents. “Our local businesses rely on access to new markets around the globe to compete,” he said.

While the House narrowly voted in favor of fast-track authority for Obama, it failed to adopt a related measure — Trade Adjustment Assistance — that would provide aid to workers who lose jobs because of free trade. Without TAA, the House trade package does not match the one approved earlier by the Senate and will not go to the president’s desk.

Rep. Earl Blumenauer (D-Ore.), who voted for both TAA and fast-track, has been singled out by Pica, the Friends of the Earth president, who says that the lawmaker “really has been there on the environment.”

Substantive issues on the environment underlie all the procedural jujitsu.

The president has said that environmental protections in the TPP are markedly better than they were in the North American Free Trade Agreement, which made them separate annexes. White House press secretary Josh Earnest said during a June 4 briefing that “this agreement would actually raise the labor and environmental standards beyond what they currently are as codified in NAFTA to a higher standard.” He said they would be “enforceable environmental standards.”

Yet the Natural Resources Defense Council, which supported NAFTA two decades ago, is now part of the coalition opposing Obama’s bid for fast-track authority. And the Sierra Club’s Solomon says the NAFTA comparison sets “an exceedingly low bar.” Friends of the Earth notes that the Office of the U.S. Trade Representative has never filed suit over an environmental issue.

A handful of TPP provisions and experience with past trade deals are motivating environmental groups.

One provision would provide automatic Energy Department approval of terminals for the export of liquefied natural gas to countries belonging to the TPP. At present, the Energy Department must determine whether such LNG export deals serve the national interest. (The Federal Energy Regulatory Commission would still need to issue separate permits.)

“This will increase pressure for more natural gas, more fracking and more pipelines and facilities to export LNG — and a tremendous amount of climate emissions,” Solomon said.

Above all, environmental groups point to the potential use of the Investor-State Dispute Settlement system by major corporations to bypass domestic courts and sue member governments to water down regulations and possibly collect monetary damages.

Conservatives and liberals such as Sen. Elizabeth Warren (D-Mass.) have expressed concern that this would violate U.S. sovereignty.

The Obama administration has argued that the dispute settlement system already exists and that the government has not lost one of the 17 investor-state cases, 13 of which went to international tribunals, over the past quarter-century.

But environmental groups say that reversals are still possible in the future and point to cases in other countries that they consider cause for alarm. Those include efforts by companies, many of them American. U.S.-based Renco would block the Peruvian government from closing down a metal smelter considered one of the world’s 10 most polluted sites; U.S-based Bilcon is seeking damages after Nova Scotia decided that blasting activities and shipping at a coastal mine would endanger marine life; Lone Pine Resources is seeking $250 million under NAFTA after Quebec imposed a fracking moratorium.

Pica said that by adding Japan, South Korea and other Asian countries as free trade partners, many major corporations would be able to turn to international tribunals and possibly take on U.S. regulations and laws.

He also notes that fast-track authority lasts for six years, covering the entire first term of the next administration. Apart from Republican candidates who largely oppose tougher environmental standards, Pica said that even leading Democratic candidate Hillary Rodham Clinton has been a strong supporter of international trade deals in the past, even as she seems to be siding with Obama’s opponents for now.

Whether environmental, labor and liberal groups can continue to block fast-track authority for Obama is up in the air. Pica said “the question over the next days and weeks is can we hold onto those votes, and I think that is anybody’s call.”