GLENWOOD SPRINGS, Colo. — A western Colorado water agency wants federal officials to hold off on reviewing a proposal to funnel water from a southwest Wyoming reservoir to Colorado's populous Front Range.

The Colorado River Water Conservation District said Friday that Colorado officials need time to study a plan by Fort Collins entrepreneur Aaron Million to divert up to 450,000 acre-feet of water a year from Flaming Gorge Reservoir.

Million's plan calls for a 400-mile, $4 billion pipeline that would take the water east across Wyoming over the Continental Divide and then south into Colorado as far as Pueblo.

The pipeline could supply enough water for up to 900,000 people a year.

The fast-growing cities along the Front Range, with an estimated 3.8 million residents, already draw water from a wide swath of the state, and many would welcome more.

Eric Kuhn, general manager of the Colorado River Water Conservation District, said Million's plan could leave less water available to western Colorado.

Water sent through Million's pipeline would count against Colorado's share of Colorado River water under interstate agreements, Kuhn said. Flaming Gorge is on the Green River, a tributary of the Colorado, which supplies much of western Colorado's water.

"We really do not know at the moment how much water is needed internally in western Colorado," Kuhn said.

Taking water out of Flaming Gorge would require a contract with the federal Bureau of Reclamation. The Colorado River conservation district board voted this month to ask the bureau to halt any work on processing the proposed contract, including an environmental study.

Wyoming water officials have also expressed reservations about whether the plan is feasible. Mike Besson, director of the Wyoming Water Development Commission, has questioned whether Colorado has legal rights to the amount of water envisioned in the plan.

Million did not immediately return a telephone message Friday.

He has called the Green River "the largest underutilized river in the West" and said his plan would benefit the Front Range's cities, agriculture and environment.