FARGO (AP) - Sen. Byron Dorgan says he thinks a method advocated by the federal government to divert Missouri River water to the Red River Valley is "a reasonable alternative."

The U.S. Bureau of Reclamation and the Garrison Diversion Conservancy District, which represented North Dakota in the process, studied six water supply alternatives for the region and said the best option involves a pipeline from the existing McClusky Canal in central North Dakota.

The $660 million option, which would bring water to the Sheyenne River and ultimately the Red River, would include a $110 million treatment plant to allay Canadian fears about invasive species entering their waters.

Former North Dakota Gov. Bill Guy and a state senator who wants to be governor are advocating a more expensive option.

Guy and state Sen. Tim Mathern of Fargo, who is seeking the Democratic nomination for governor, say they favor an option that would include a pipeline from Bismarck to Fargo, roughly paralleling Interstate 94. That option would cost more than $1 billion.

The less-costly option would require more water because of the loss of water to evaporation and seepage in the open canal, and would be more susceptible to pollution or deliberate contamination, Guy and Mathern say.

Whatever option ultimately is chosen, there is no guarantee the project will be built. Congress must still provide funding, and there is opposition to the project from Canada and the states of Missouri and Minnesota.

"The battle will be on the authorization side," not necessarily the funding side, said Dorgan, D-N.D. "It will not be easy."

Dorgan last week asked Secretary of State Condoleezza Rice to step into disputes between North Dakota and Canada over the diversion of Missouri River water. Canadian officials fear that invasive species might enter their waters not only because of the Red River Valley Water Supply Project, but also the Northwest Area Water Supply Project.