Arizona won’t have all the pieces of a Colorado River drought plan finished by the federal government’s deadline to finalize protections for water used by millions across the U.S. West, state water officials said Tuesday.

It’s the latest hurdle threatening the plan between seven states to take less water from the drought-starved Colorado River, which supplies 40 million people and 5.5 million acres of farmland. Missing the March 4 deadline could allow the federal government to step in and decide the rules.

About half of the 15 agreements that Arizona needs to secure among water users will be ready by March 4, said Ted Cooke, director of the Central Arizona Project, which brings Colorado River water to the sprawling cities and farm fields around Phoenix and Tucson.

“That’s an artificial deadline, and these are very complex agreements and very complex negotiations, and we will take the time that we need to do them properly,” Cooke told reporters Tuesday following a meeting of water users working on the drought plan.

He said he hopes to finalize all the agreements within 60 days.

Wyoming, Colorado, New Mexico, Utah and Nevada have joined drought contingency plans for the Colorado River, while Arizona and California are still working on plans.

Arizona lawmakers have approved the drought plan, but U.S. Bureau of Reclamation Director Brenda Burman has said the state also must finalize the complex agreements needed to implement it.

If that’s not done by March 4, Burman says she will ask governors what should happen next — starting a process that could result in federally mandated cuts instead of the voluntary plans negotiated by the states. That’s particularly worrisome in Arizona, which has the lowest-priority water rights on the Colorado River.

Cooke repeatedly declined to speculate on what would happen if the state doesn’t finish its work by the deadline. But he said Arizona would probably be done before the federal government could get very far down an alternative path.

Meanwhile, lawmakers planned to debate a measure that has angered the Gila River Indian Community, a key player in several of the agreements that the state is trying to finalize. The tribe has said it will back out of the drought plan without assurances that the legislation will die.

The legislation would alter the state’s “use it or lose it” water rights law, which the tribe says would undermine its rights to water from its namesake river.

“The community cannot be singled out for legislative attack by the most powerful members of the Arizona House of Representatives and still view itself as a genuine partner in solving the state’s water crisis,” Gila River Gov. Stephen Roe Lewis said. “We view this as slap in the face of the community.”

House Speaker Rusty Bowers, who sponsored the legislation, said he’s trying to protect the livelihood of landowners from the tribe’s lawsuits.

FILE - In this July 28, 2014, file photo, lightning strikes over Lake Mead near Hoover Dam that impounds Colorado River water at the Lake Mead National Recreation Area in Arizona. (AP Photo/John Locher, File)
FILE – In this July 28, 2014, file photo, lightning strikes over Lake Mead near Hoover Dam that impounds Colorado River water at the Lake Mead National Recreation Area in Arizona. (AP Photo/John Locher, File)