Pipeline company TransCanada said it was filing an application with state regulators in Nebraska to build Keystone XL, ending a bid to challenge eminent domain.

Spokesman Mark Cooper said in an emailed statement the company was ready to file an application with the Nebraska Public Service Commission for pipeline construction.

"We believe that going through the Public Service Commission process is the clearest path to achieving route certainty for the Keystone XL project in Nebraska," he said. "It ultimately saves time, reduces conflict with those who oppose the project and sets clear rules for approval of the route."

The company said it was moving its petitions to the state regulator after withdrawing from a lawsuit filed by Nebraska landowners challenging the company's claim to eminent domain for land intended for the Keystone XL pipeline.

Lancaster County District Court Judge Stephanie Stacy in February 2014 ruled a state law granting power of eminent domain to former Gov. Dave Heineman was unconstitutional. State law LB 1161, passed in 2012, gave the governor authority over the Keystone XL route from Canada through the state instead of the Nebraska Public Service Commission.

Environmental campaigners pressured pipeline planner TransCanada to revise the Keystone XL route through the state to avoid a sensitive aquifer. Heineman in 2013 said he was satisfied a revised route for the tar oil sands pipeline avoided the Sand Hills aquifer.

The state Supreme Court in January, in Thompson v. Heineman, said the majority opinion was on the side of the landowners in the case, though because not all judges sat for the decision, the legislation stood by default.

The U.S. State Department, tasked with the federal vetting process, said the January ruling was one of the issues standing in the way of the pipeline review. TransCanada submitted an application to build the pipeline through the United States more than seven years ago.

Jane Kleeb, director of pipeline opposition group Bold Nebraska, said TransCanada's decision to pull out of the latest legal battle in the state shows the odds are stacked against Keystone XL.

"They've recognized that they've lost in Nebraska," she said in a statement.

Bold Nebraska estimates the new review process could take at least a year.

Supporters of Keystone XL say it would ensure North American energy security and provide a source of economic stimulus. Opponents question those claims and state the heavier type of crude oil meant for Keystone XL is too much of an environmental risk to support.