WASHINGTON — The State Department on Monday denied claims of "complicity" with a firm building a $7 billion US-Canada oil pipeline, made by an environmentalist group that released emails it said showed bias.

The State Department insisted it had behaved "transparently and evenhandedly" toward the Keystone XL project to bring oil from Canada's tar sands to the US Gulf Coast, which has prompted repeated protests.

In a long-awaited environmental impact statement on the project, the State Department said in August that the pipeline would be safer than most current oil transportation systems.

But Friends of the Earth on Monday circulated what it sees as incriminating emails between Marja Verloop, who works at the US embassy in Ottawa, with Paul Elliott, the Washington lobbyist for pipeline operator TransCanada.

The group said the emails, part of a second batch obtained through a Freedom of Information Act request, reveal "department employees' pro-pipeline bias and complicit relationships with industry executives."

Friends of the Earth highlighted Elliott's former job as national deputy director of Secretary of State Hillary Clinton's failed 2008 presidential campaign.

In one email sent in September last year, Verloop took on a congratulatory tone with Elliott after he announced that Democratic Senator Max Baucus supported the pipeline project.

"Go Paul! Baucus support holds clout," according to Verloop's message.

Other emails between Verloop and Elliott had "smiley face" tags, which Friends of the Earth said shows the friendly attitude toward TransCanada.

The Keystone XL project, due to stretch across 1,700 miles (2,700 kilometers) and transport up to 800,000 barrels of Canadian tar sands crude to the US Gulf Coast a day, is part of a broader $13 billion pipeline system.

In another email exchange, Verloop told TransCanada that some controversial aspects of the project, withdrawn for now from the dossier, could be re-introduced after the administration gives the go-ahead.

Clinton's spokeswoman Victoria Nuland said Friends of the Earth's FOIA request itself was "one-sided" because it only sought information about Verloop's conversations with Elliott, failing to show "far broader" exchanges that also engaged the Canadian government and non-government organizations.

"I would also say that Ms. Verloop herself didn't have any impact or any input in the development of the Keystone environmental impact statement," Nuland told reporters.

"Our view on this from beginning to end is that this department, our folks in Ottawa, behaved transparently and evenhandedly with regard to all the groups involved in this topic."

President Barack Obama is due to take a final decision by the end of the year.