Newly disclosed emails suggest senior policy officials at the Environmental Protection Agency and environmental groups are working closely to kill the Keystone XL pipeline, critics say.

"These damning emails make it clear that the Obama administration has been actively trying to stop this important project for years," Sen. John Barrasso, R-Wyo., who has long advocated for the Canada-to-Texas pipeline's construction, said in a statement to Fox News.

The emails were obtained under a Freedom of Information Act request by the Energy and Environment Legal Institute. In one communication, Lena Moffit of the Sierra Club wrote to three senior policy staffers at the EPA, including Michael Goo, who was then the associate administrator for policy.

"Thanks so much for taking the time to meet with us on Keystone XL yesterday," she wrote. "Let me know if I can be helpful in any way -- particularly in further identifying those opportunities for EPA to engage that don't involve 'throwing your body across the tracks,' as Michael put it."

EELI senior legal fellow Chris Horner told Fox News that as a government agency, EPA couldn't be seen as overtly trying to kill Keystone, but was reaching out to environmental groups for other ideas on how to do it.

"On its face," Horner told Fox News, "it smacks of classic secret dealing and an uncomfortably close working relationship and one that is known to these parties, but quite plainly not advertised to the public."

Barrasso was less diplomatic. "Despite the fact that Keystone XL has bipartisan support in Congress and from governors, environmental extremists inside and out of the administration are working behind closed doors to kill it," he said.

Many EPA staffers -- including Goo -- came from the environmental movement. Goo, who is now at the Department of Energy's policy shop, was with the Natural Resources Defense Council.

Horner said many EPA staffers share a policy agenda with environmental groups, a common cause illuminated in the emails his group obtained.

"This series of correspondence plainly indicates that you've got an agency that's made up its mind -- working with allies with whom it is ideologically and substantively aligned on this -- trying to find ways to advance their argument without being too obvious about it," Horner told Fox News.

Emails previously obtained by Horner's group reveal similar agenda-sharing regarding coal. There are dozens of exchanges on the just-released regulations regarding coal-fired power plants.

In one email, John Coequyt, head of Sierra's "beyond coal" campaign, wrote to Goo and another EPA staffer in an apparent attempt to pressure EPA into adopting regulations so strict that coal plants that already received construction permits could not be built.

"Attached is a list of plants that the companies shelved because of uncertainty around GHG regulations. If a standard is set that these plants could meet, there is a not small chance that they (sic) company could decide to revive the proposal," Coequyt wrote.

In another email to Goo and Alex Barron of EPA's climate office, Coequyt responded comically to an August 2012 article that quoted now-EPA administrator Gina McCarthy as saying the new regulations would not kill coal.

"Pants on fire," wrote Coequyt

Other communications arranged meetings between Goo and Coequyt at the Starbucks in the JW Marriott hotel on Pennsylvania Avenue, close to the EPA -- an attempt, charges Horner, to discuss issues without having to sign into the EPA building. And there are numerous requests from environmental groups to meet with EPA staffers.

There is also evidence, said Horner, that EPA officials sought to keep their deliberations with environmental groups out of the public record by using private email accounts and back-channel communications.

In one such exchange, James Martin, who was the EPA's Region 8 administrator, exchanged ideas with the Sierra Club's chief legal counsel Vickie Patton on where to hold public hearings on new coal regulations. Martin used a ".me" account instead of his official EPA server.

Martin resigned in February of 2013 in a storm of controversy over using personal email to conduct official communications.

Many of the emails provided to Fox News have been redacted. The EPA claimed they show the "deliberative process." Now that the proposed regulations on coal have been published, Horner and the Energy and Environment Legal Institute plan to go to court to obtain unredacted versions.