BILLINGS, Mont. - A proposed railroad that would open southeastern Montana's isolated coal fields to mining hit another delay Wednesday, even as its developer released a new and sharply higher cost estimate.

The 121-mile line could cost $600 million, nearly double earlier estimates, said Tongue River Railroad developer Mike Gustafson. The new price tag comes as the Montana Fish, Wildlife and Parks Commission declined to grant a 25-acre easement sought by the railroad for now.

Commissioners said they were uncomfortable with a tentative deal to let the railroad pass through a state fish hatchery in Miles City where endangered pallid sturgeon are raised. They said they would revisit the issue after negotiations with the railroad. No date was set.

The easement, the first of nine needed by the railroad from the state, is considered key for a project on the drawing boards since the early 1980s. The railroad received final approval from the U.S. Surface Transportation Board in 2007 following years of litigation.

Railroad developer Gustafson said he would continue to push his easement request.

"This is going to establish a style as far as how Tongue River Railroad deals with property owners," he said. "We're frustrated, but the better way to do this is to take these issues that have been raised" and continue to negotiate.

The delay marks at least a temporary win for railroad opponents, who don't want the line to slice through an estimated four dozen ranches.

The project also has been fought by environmental groups over its potential to open billions of tons of coal to mining. That includes reserves controlled by the state, the Northern Cheyenne Indian Tribe and private owners.

If Montana wildlife commissioners fight the railroad, the route through the hatchery still could be claimed through condemnation under federal law.

Attorneys for the state said condemnation would leave the commission with less room to negotiate an agreement that could protect the hatchery.

"Unfortunately, this is where it will go, if it goes in at all," said Rebecca Jakes Dockter, an attorney for the state's Fish, Wildlife and Parks Commission who helped negotiate a tentative easement deal with the railroad.

Hatchery officials reiterated their opposition to the project, citing possible derailments and vibrations from coal trains that could disrupt breeding sturgeon and other fish.

The state's tentative easement deal had called for the 51-year-old hatchery to be insured by the railroad for $25 million.

Commission chairman Shane Colton said he preferred a $5 million bond, to increase the chances of the hatchery being compensated if it were ever damaged.