By MATTHEW BROWNBILLINGS, Mont. (AP) â¿¿ Opponents of a railroad that would open Montana's coal fields to new mining have asked federal officials to halt their review of the proposal, alleging it would be much larger than disclosed with impacts stretching to the West Coast. The project also is drawing increased scrutiny in Washington state, where officials expressed worry that coal export traffic could further strain crowded rail lines. The Tongue River Railroad would haul roughly 20 million tons of fuel annually from a planned Arch Coal Inc. strip mine near the Northern Cheyenne Indian Reservation, according to its backers. It's been billed as a major economic boost for remote southeastern Montana. But opponents said Thursday they want to turn the spotlight on the potential for the $416 million railroad to spur more mining of coal for export to Asia, along a route through Montana, Idaho and Washington state. They allege the railroad's owners intentionally played down the scope of the project by saying it would haul an average of 7.4 full and empty coal trains a day. That figure counts only Arch's immediate mine plan. A second rail spur proposed as part of the railroad's application would give access to additional coal fields. At least one mine, the Montco Mine, was previously proposed in that area. The Northern Cheyenne also have had discussions with companies about mining. The railroad acknowledged the potential for additional mines in its Dec. 17 application for federal approval. They did not provide any potential volumes. A spokeswoman for railroad co-owner BNSF Railway Co. said Thursday that the company counted only coal coming from Otter Creek because it is the only mine currently pending. Arch referred questions to BNSF. If more mines were built, traffic on the Tongue River Railroad could quickly top the government's higher-impact threshold of eight trains daily.