CALGARY -- Nebraska's Public Service Commission has approved the passage of TransCanada's Keystone XL pipeline through the state in a 3 to 2 vote, but not along its preferred route for the controversial $10 billion project.

The panel has voted for the proposed mainline route, which follows the company's preferred route for the north of the state before veering further east to more closely align with TransCanada's existing pipeline in the state.

In a written decision, the panel said it was in the public's interest to put the new pipeline nearer to the current one to maximize monitoring resources, to impact less of the habitat of endangered species, and other route benefits.

The panel said in the decision that the alternative route was only eight kilometres longer than the preferred route, and that TransCanada (TSX:TRP) had told the commission it was still a viable and beneficial route.

Still, those opposed to the project jumped on news of the alternative route by saying it could bring into doubt the future of the project.

"Today's decision is no guarantee that this pipeline will ever be built," said Greenpeace campaigner Mike Hudema in a statement.

"Nebraska opted not to give TransCanada its preferred route through the state, so the company now has more hurdles in front of its beleaguered pipeline."

The panel's approval came with a tight margin of victory for the pipeline, which would transport about 830,000 barrels of oil a day from Hardisty, Alta. to Steele City, Neb.

Commissioner Crystal Rhoades, who voted against the project, said she did so for several reasons including that TransCanada had not proven that it could not use the same route as its existing pipeline through the state.

"The applicant did not refute the landowners argument that using the existing Keystone One would avoid fragile soils, reduce impacts to endangered species, and avoid widespread controversy and opposition to this project."

Rhoades, the only commissioner to comment before the vote, said she was also voting no because the proposed pipeline route violates the due process of landowners, had not been studied enough, runs near the sensitive Sandhills ecological region and the Ogallala aquifer, does not provide enough economic benefits for the state, and the company hadn't consulted with Native Americans in the state.

The vote comes as TransCanada continues to clean up a 5,000-barrel oil spill from its pipeline in nearby South Dakota that opponents have held up as a reason not to approve Keystone XL.

The commission, however, was specifically prohibited from evaluating safety considerations, including risk or impact of a spill, and ruled instead on issues including regulatory compliance, economic and social impacts of the project, the potential intrusion on natural resources, and whether better routes exist.

Barack Obama rejected Keystone XL in 2015 after years of review, only for President Donald Trump to give the go-ahead to the project in March, saying the pipeline will bring jobs and reduce dependence on foreign oil.