LAS VEGAS (AP) - The Energy Department is refocusing plans for a cross-Nevada railroad to a national nuclear waste repository, after an Indian tribe said it won't let radioactive waste cross its reservation, a top Yucca Mountain official said.

A north-to-south railroad corridor that would have crossed the Walker River Paiute reservation in Mineral County no longer will be considered, Ward Sproat, director of the Office of Civilian Radioactive Waste Management, said Wednesday.

The department will instead focus on completing studies of the so-called Caliente rail corridor, a 319-mile route that would be built from eastern Nevada across the state to the Yucca Mountain repository at a projected cost of more than $2 billion.

Sproat made his comments during a presentation in Washington, D.C., to a conference organized by the U.S. Transport Council, whose members are tied to the shipping of nuclear materials.

Sproat, the Energy Department's Yucca project chief, said it was too late to remove the 280-mile Mina corridor from an environmental impact study the department expects to make public in October.

He said the Mina route could have been cheaper and faster to build, but said planners now expect the decision will favor the Caliente route.

The Walker River Paiute tribe announced April 17 that it was withdrawing from environmental studies of the Mina route, named after a site south of Hawthorne.

The tribe's participation was key to Energy Department plans to use existing railroad rights-of-way through old mining districts to Yucca Mountain, 90 miles northwest of Las Vegas.

Bob Halstead, a transportation consultant to the state of Nevada, said the Energy Department might face difficulties trying to develop the east-west Caliente route.

Halstead said planners face several engineering challenges along the route, plus resistance from some ranchers and from the sponsors of a monumental desert art exhibit in Garden Valley.

The Energy Department plans to use the rail line to ship materials to Yucca Mountain, where it plans to entomb at least 77,000 tons of the nation's most radioactive waste in tunnels.

Congress picked the Yucca site in 2002, with plans to open it in 2010. But budget cuts and questions about quality control have stalled the Energy Department schedule for seeking an operating license from the Nuclear Regulatory Commission.