The controversial Keystone XL pipeline moved one step closer to approval after the U.S. State Department concluded that the project would not significantly impact greenhouse emissions.

A report by the department, released Friday, clears a major hurdle for the development of the $7-billion pipeline. But U.S. President Barack Obama has the final say.

The Environmental Protection Agency and other departments now have 90 days to comment before the State Department makes a recommendation to Obama.

The report says the development of the Alberta oilsands will occur regardless of whether the pipeline is built.

Canada鈥檚 Natural Resources Minister Joe Oliver said Friday that he is 鈥渆ncouraged鈥 by the findings. 

鈥淭his is the fifth federal study on the environmental impact of the Keystone XL pipeline. Each previous one has stated that building Keystone XL would not adversely affect the environment,鈥 he told a news conference. 鈥淭oday鈥檚 report confirms once again this result, including no appreciable impact on greenhouse gases.鈥

But Green Party Leader Elizabeth May said the State Department鈥檚 report 鈥渄oes not say that one can build the Keystone pipeline and not increase greenhouse gases.

鈥淯nder certain scenarios you can, and under other scenarios you can鈥檛,鈥 she told 麻豆影视 Channel Friday, calling the report 鈥渢epid,鈥 rather than a green light for the pipeline project.

The proposed pipeline would carry bitumen from the Alberta oilsands to a hub in Nebraska, where it would connect with existing pipelines that lead to refineries in Texas.

The Canadian government says the pipeline will create 鈥渢ens of thousands of jobs鈥 and give Canada鈥檚 oil exports a major boost.

鈥淭he choice for the United States is clear: oil supply from a reliable, environmentally responsible friend and neighbour or from unstable sources with similar or higher greenhouse gas emissions and lesser environmental standards,鈥 Oliver said in his statement Friday.

He later told CTV鈥檚 Power Play that Keystone XL would be 鈥渆nhancing North American energy independence.鈥

Environmental groups on both sides of the border are strongly opposed to the project, saying that stopping the pipeline would thwart oilsands development.

But the State Department report rejects that argument.

"The dominant drivers of oilsands development are more global than any single infrastructure project," the report's executive summary said.

In a statement, Alberta Premier Alison Redford said her government welcomes the State Department鈥檚 鈥渢horough environmental analysis.

鈥淭he findings are consistent with the analysis Alberta has put on the table in our various face-to-face meetings with key decision makers in Washington and our submissions made on this important file,鈥 she said. 鈥淚鈥檓 pleased that by respecting and actively participating in the process, our input has been accepted and understood.鈥

Green Party hopes Obama will say 鈥榥o鈥

Still, May said she doesn鈥檛 believe that a thorough review of the latest report will give Obama and his administration the assurances they need about Keystone XL.

鈥淚n the interest of Canada and in the interest of climate change, I sure hope Barack Obama says no,鈥 she said.

The Environmental Defence group also said that the report shows the pipeline will fail Obama鈥檚 鈥渃limate test.鈥

鈥淜eystone XL is all risk and no reward for Canadians, Americans and our shared climate,鈥 executive director Tim Gray said in a statement.

鈥淭he bottom line is that it will never be easy to build another giant pipeline in North America. There is too much at stake.鈥

Two years ago, Obama blocked Keystone XL, saying there wasn鈥檛 enough time to fairly review the pipeline鈥檚 impact. His decision created some tension between Canada and the U.S.

Asked Friday whether the Canadian government has been frustrated by the 鈥渇oot-dragging鈥 of the U.S. administration, Oliver said: 鈥淭his isn鈥檛 a day for frustration or exasperation.鈥

The New Democrats denounced the latest development in the Keystone saga Friday, calling the pipeline a 鈥渟hort-sighted鈥 project.

鈥淭he Conservative government鈥檚 bumbling approach to oil sands development has given Canada a black eye and hurt our relationship with our closest ally,鈥 NDP鈥檚 natural resources critic Peter Julian said in a statement.

鈥淭his report highlights how oil from the oil sands is more greenhouse gas intensive, yet the Conservatives have stalled regulations for the oil and gas sector for years.鈥

Opponents say they won鈥檛 give up

A number of groups and residents opposed to Keystone XL in the U.S. are threatening to stall the pipeline project with legal action.

Anti-Keystone landowners in Nebraska are already taking their state government to court over the issue.

An internal investigation is also underway at the State Department over conflict-of-interest allegations against contractors who worked on the pipeline report, but had also done work for Keystone builder TransCanada Corp.

Meanwhile, a spokesperson for U.S. Secretary of State John Kerry said there is 鈥渢echnically鈥 no deadline for when he needs to make a recommendation to Obama about the pipeline.

New pipeline ad surfaces

On the same day the State Department released its report, a new ad by the Conservative government was posted on YouTube, touting the report鈥檚 findings and the pipeline鈥檚 benefits.

鈥淎merican billionaires are using their wealth to attack our oil industry,鈥 the voiceover in the ad says, referring to wealthy Keystone opponents.

Tom Steyer, a San Francisco billionaire who is also a major Democratic party fundraiser, has been a major crusader against the construction of the pipeline.  

The ad also slams the 鈥渄istortion of facts鈥 and 鈥渇ear-mongering.鈥

Oliver told Power Play that the government wanted 鈥渢o straighten the record,鈥 especially following what he called a 鈥減reposterous ad鈥 that recently aired on a U.S. network.

The ad, put together by NextGen Climate Group, which is led by Steyer, highlighted Chinese investments in Canadian natural resources and accused the two countries of conspiring to 鈥渟ucker punch鈥 the American heartland.

With a report from The Canadian Press and The Associated Press