FLAGSTAFF, Ariz. (AP) – Sen. Jon Kyl has helped negotiate and shepherd key water rights settlements through Congress, but a roughly $800 million price tag and the political climate are threatening a northern Arizona deal, according to court documents.

The Arizona Republican has asked negotiators for the Navajo Nation, the Hopi Tribe and 30 other entities to try to lower the cost by next month so that he can introduce legislation well ahead of his planned retirement.

Kyl's office did not return repeated email and phone messages, but court documents outline the concern about the settlement that would quantify the Navajo Nation's rights to water from the lower Colorado River basin in Arizona and settle the Hopi's claims.

“We are turning our attention to focus on what might be possible during Sen. Kyl's tenure,” Stanley Pollack, the Navajo Nation's water rights attorney on the case, told The Associated Press.

No one will say what figure the negotiators are aiming for or how the settlement might be tweaked, citing the confidential nature of the talks.

Congress has enacted more than two dozen American Indian water rights settlements since 1978, some of which have cost hundreds of millions of dollars apiece. Tribes often trade what could be huge water claims for the promise of federal funding to deliver the water to tribal communities.

A handful of cases have been resolved through litigation.

The Navajo Nation was the first to sign the agreement last November that also requires the approval of the Hopi Tribe, the state and its major water providers, cities, ranches and ultimately, Congress. If the price tag or other terms change, the document would have to go back to the Navajo Nation Council for approval.

The settlement as is would give the Navajo Nation 31,000 acre-feet of water a year from the lower Colorado River basin, any unclaimed flows from the Little Colorado River, and nearly unlimited access to two aquifers beneath the reservation.

Kyl, a former attorney specializing in water law, helped secure water rights for the Gila River Indian Tribe in a historic 2004 agreement and for the White Mountain Apache Tribe, which received $292 million for a rural water system.

“He's a powerful, powerful figure, and for him to have agreed to something in the fall of 2010 and to have to tell the (Hopi) Tribe and the (Navajo) Nation the amount is too high, that says the political landscape has profoundly changed,” said Robert Glennon, a law professor at Arizona State University and author of “Unquenchable: America's Water Crisis and What To Do About It.”

The northern Arizona proposal is a result of more than a decade of negotiation among more than 30 entities. The $800 million would go to pipelines that would deliver water to the Navajo and Hopi reservations that others could tap into.

The settlement would end a lawsuit the Navajo Nation filed against the U.S. Department of Interior in 2003 asserting rights to water from the Colorado River. A 1922 river compact recognizes tribal water rights, but the potentially huge claims are not quantified.

“That's what we're trying to accomplish here,” said Dave Roberts, water resource manager for the Salt River Project, metro Phoenix's largest water provider. “The fact that they are early and the amount is unquantified introduces a great deal of uncertainty in regard to the validity and extent of others using the same water source.”

The Navajo and Hopi tribes also are party to a separate case in Apache County Superior Court concerning water rights from the Little Colorado River. Both the federal court and state court have granted repeated stays to allow for settlement negotiations.

A spokeswoman for Rep. Paul Gosar, whose district includes the Navajo Nation, said that Kyl has been leading the talks to bring down the price and that Gosar would continue to monitor them.

Staff from Rep. Trent Franks' office met with the Hopi Tribe last week to discuss the settlement. A spokesman did not immediately return a message left by The Associated Press.

Critics have said the Navajo Nation shouldn't waive its future claims to the water and should demand more. Supporters cite the need to get running water to parts of the reservation that have long lived without it.

“We have to find a way to pipe the water to them,” said Navajo lawmaker Joshua Lavar Butler, whose constituents live on the western side of the reservation. “(But) we may have to take cuts here and there from the entire project.”