The US State Department issued its final supplemental environmental impact statement for the Keystone XL project last month.

While it endorsed the project it is not likely to speed up the approvals process it still has to go through.

This, some fear (and others will no doubt rejoice), may make the project irrelevant and the window for the project to get off the ground is fast closing.

So it appears, in one way, that the green groups have had a win.

However - and here is some delicious irony - while they may stop the pipeline they will not stop the flow of crude.

The same amount of crude will still find its way down to the Gulf of Mexico. The oil sands business will flourish.

The net greenhouse gas emissions will grow because trains, instead of a pipeline, are being used to shift it.

Producers, it seems, are quite happy to use trains to move their crude - a transport method that will have a greater greenhouse gas emissions footprint than a pipeline would.

The release of the State Department report starts a 30-day public comment period and turns the permitting review process over to President Barack Obama.

For its part, project proponent TransCanada says the State Department report clears the way for the project.

"The environmental analysis of Keystone XL, released January 31, once again supports the science that this pipeline would have minimal impact on the environment," TransCanada president and CEO Russ Girling said.

"The next step is making a decision on a presidential permit for Keystone XL.

"I believe that this project continues to be in the national interest of the US for two main reasons: supporting US energy security and the thousands of jobs our multi-billion dollar project will create."

Girling added that according to the US Energy Information Administration and the International Energy Agency, the US would still require millions of barrels of oil imported every day to meet its own needs for decades to come.

He argued that Americans continued to support the pipeline, saying that over the past three years more than 15 polls had indicated the majority of Americans supported the pipeline.

"It was North American producers and refiners who asked TransCanada to build Keystone XL and connect their refineries with Canadian and US oil fields," Girling said.

"They need the oil from this pipeline system to create products we all rely on - fuel for our vehicles, heat and air conditioning for our homes, diesel for farm tractors and heavy equipment and thousands of consumer products that are made from petroleum-based products."

Girling argued the pipeline was not about energy versus the environment but rather about where Americans wanted to get their oil.

"Keystone XL will displace heavy oil from places such as the Middle East and Venezuela and of the top five regions the US imports oil from, only Canada has substantial gas regulations in place."

TransCanada has entered into contracts for Keystone XL with more than 50 suppliers across the US and invested more than $US2 billion ($A2.2 billion) to purchase materials and related services.

The environmental groups are not taking the State Department's report lying down. Delaying tactics are part of their agenda.

NextGen Climate Action president Tom Steyer wrote to US Secretary of State John Kerry urging him to launch an "independent review of the work product contained in the Keystone XL pipeline impact statement".

"Of particular concern are final supplemental environmental impact statement conclusions that conflict with, and are contradicted by, tar sands industry executives who confirm that they need the pipeline in order to continue to develop the tar sands and to reach international markets," he writes.

For its part the Sierra Club is rattling the tin to raise funds to fight what it believes will be a hard court press from the oil industry.

"To be frank, there's no guarantee the right decision will be made without you and while the end's in sight, we're running out of time," Sierra Club executive director Michael Brune wrote to members.

He says that with "big oil pouring millions into clouding the truth we have to come out in full force. Make a gift to Sierra Club today".

While green groups are frantically trying to rally support, it appears they may have already won.

A research report from Barclays shows the bank believes the Keystone train may have already left the station.

Its note says the State Department report may hearten pipeline supporters but "despite this seemingly strong endorsement, we believe that the path to final presidential approval will not be entirely smooth".

Barclays says the report affirms the State Department's position that Canadian crude will find its way to market anyway, pipeline or no.

"In our view the president has sufficient justification to approve, reject or request modification to the permit," the bank says.

"Even in a scenario in which the pipeline is approved, complying with new environmental criteria would inflate costs and possibly reduce the viability of the Keystone XL route, relative to rapidly evolving rail-based transport options.

"A scenario in which further skirting of the Ogallalla aquifer is required could delay the pipeline further and even possibly raise costs."

Barclays believes rail might emerge as the solution - a view it says has been supported by producers.

"Though we have not seen exponential take-off of crude by rail in Canada on the scale of that in North Dakota, state's analysis shows there are no significant barriers to this happening in the next couple of years," the bank says.

The Keystone XL project would consist of 1400km, 900mm pipeline and related facilities for transport of crude oil from the Western Canadian Sedimentary Basin and Bakken crude from an oil terminal near Baker, Montana.

The pipeline would take the oil to pipeline facilities near Steele City, Nebraska and from there it would be carried to refineries on the Gulf of Mexico.