SACRAMENTO, Calif. — After months of behind-the-scenes negotiations, California has an answer to six other western states sharing the Colorado River: Get lost.

The proposal California offered Tuesday makes no significant concessions to demands from its neighbors — asserting higher priority senior water rights to the largest share of the river that have been enshrined in an agreement dating back decades.

That leaves it to the federal government to try to find a resolution.

“The states are not going to reach an agreement. We are just too far apart,” said Rep. Greg Stanton (D-Ariz.), who represents the Phoenix area. “Now is the time that we need this administration to come up with a solution to this dilemma, and we need it now.”

California is insisting on its legal claims under a compact dating back to 1922 as the river faces unprecedented strain because of climate change and population growth in the Southwest. The standoff thrusts the Biden administration into the position of deciding how to resolve competing claims on water shared among 40 million people from Wyoming to Mexico.

The Interior Department, which asked the states to come up with a joint plan to reduce use by roughly 30 percent, is expected to impose cuts as early as this summer.

Water flows down the Colorado River downriver from Hoover Dam in northwest Arizona, on Aug. 14, 2022, near the Lake Mead National Recreation Area.