LINCOLN, Nebraska — Opponents of TransCanada Corp's proposed Keystone XL oil pipeline argued on Tuesday that regulators in Nebraska had no authority to approve the line's "alternative" path through the state, and that the project should be considered dead.

The Nebraska Public Service Commission issued an approval for the line to pass through the state in late November, removing what appeared to be the last big regulatory obstacle for the long-delayed project backed by President Donald Trump.

But the commission's approval was not for the route TransCanada had singled out in its application, but for an alternative that shifts it closer to an existing pipeline right-of-way down the eastern side of the state.

David Domina, an attorney for landowners along the Keystone XL route, argued at a hearing in front of the commission on Tuesday that the regulatory body was only allowed to approve or deny TransCanada's preferred route.

He said that many landowners along the alternative path had not been notified a pipeline might be crossing their property, and that the specific social and environmental impacts of the alternative path had not been properly studied.

Tuesday's hearing was set after TransCanada filed a motion with the commission asking if it could amend its initial application, in a move to head off legal challenges to the approved route.

"By filing a new application, we are working to reduce the possibility of the PSC decision being overturned which would compromise our ability to build this project on time and on schedule," a spokesman for the company told Reuters.

Pipeline opponents say that request should be denied because the Nebraska regulatory body's statutes do not allow for retroactive amendments to such applications. The commission is considering TransCanada's new application request.

The proposed line, which would run about 1,899 km from Hardisty, Alberta, to Steele City, Nebraska, has been a lightning rod of controversy. Since it was proposed a decade ago, environmentalists have made it a symbol of their broader fight against fossil fuels and global warming. Business groups and Trump say it could lower fuel prices and create employment.

Trump handed TransCanada a federal permit for the pipeline in March as part of a broader agenda to boost the energy sector. That reversed a decision by former U.S. President Barack Obama in 2015 to block the project on grounds it would not bring significant enough economic benefits to outweigh its environmental impact.