The company behind the massive Keystone XL oil pipeline from Canada to the US Gulf Coast has asked the US state department to suspend its review of the controversial project.

Calgary-based TransCanada said on Monday that the pause is necessary while it negotiates with Nebraska over the pipeline's route through the state.

Environmental activists swiftly denounced the request as a bid to dodge a near-certain rejection of the pipeline, the New York Times reported on Tuesday. Allowing the delay would push off the decision on the project until after the 2016 presidential election.

"We have just received TransCanada's letter to Secretary Kerry and are reviewing it. In the meantime, consideration under the Executive Order continues," a state department spokesperson said.

TransCanada's request for a pause points to a Nebraska regulatory process that could take another seven to 12 months. 

The move might delay a decision until the next US presidential election on November 8, 2016.

The review is mandated as part of the application process because the pipeline crosses an international border.

The state department does not have to grant TransCanada's request for a pause and instead can go on with the review process.

'Extra time'

Ahead of TransCanada's announcement on Monday, the White House said that US President Barack Obama intended to rule on the 1,900km long pipeline before he leaves office in January 2017, without giving any details on the timeline, however.

The project has had little support from the Obama administration in the past.

All of the leading Democratic presidential candidates, including Hillary Clinton, have already gone on record to oppose the pipeline, while all the main challengers for the Republican nomination support it.

Obama is expected to make a decision on the pipeline before the end of his presidency [Pablo Martinez Monsivais/AP]

Environmental groups have long opposed the project that would carry dense oil from the "tar sands" of central-western Canada, diluted with benzene.

Some activists are now saying that TransCanada wants to delay the review process in hopes that a more sympathetic Republican administration will move into office in 2017.

"In defeat, TransCanada is asking for extra time from the referees, and clearly hoping they will get a new head official after the election. It's time for the current umpire, President Obama, to reject this project once and for all," environmental activist Bill McKibben, co-founder of the group 350.org, told the AP news agency.

Flashpoint

For seven years, Keystone has been a flashpoint in the US debate over climate change and energy security. 

Critics oppose the concept of tapping the Alberta oil sands, saying it will require huge amounts of energy and water and increase greenhouse gas emissions.

They also raise concerns that pipeline leaks could potentially pollute underground aquifers that are a critical source of water to farmers on the Great Plains.

Pipeline supporters insist it will create jobs and boost energy independence. They also say pipelines are a safer method of transporting oil than trains, pointing to recent cases of oil train derailments.

TransCanada spokesman Mark Cooper denied that the request for a pause in the review has anything to do with an expected rejection of the pipeline application by the Obama administration, but acknowledged they "have been hearing since February the same rumours that a denial or a decision is imminent".

"Our focus remains on continuing to demonstrate the project is in the interest of the US," Cooper said.

"Our focus isn't on the political machinations of what this president may or may not do or who may be in office a year from now."

Source: Al Jazeera and agencies