A resolution may not come until next year in lawsuits filed by Canada and the state of Missouri that challenge North Dakota's plan to divert water from the Missouri River to the state's northwest communities, the project's manager said Monday.

U.S. District Judge Rosemary Collyer delayed by a month the state and federal government's mid-July deadline for filing legal briefs on the Northwest Area Water Supply project. She said a new Justice Department attorney on the case needs more time to prepare.

Attorneys for North Dakota still hope to persuade Collyer to allow some new work to begin on the NAWS project this summer. Those arguments won't come until the briefs are filed by the new deadline of Aug. 13.

Officials are looking to upgrade a plant in Minot where river water would be treated to drinking standards.

"There is some planning and designing work that we'd like to be able to start," said Michelle Klose, the project's manager for North Dakota's Water Commission.

The Northwest Area Water Supply project has been under construction since 2002. It faces lawsuits by officials in the Canadian province of Manitoba, who worry harmful organisms could be transferred to their waters, and the state of Missouri, which fears a depletion of the river that forms its western border.

The lawsuits have been combined under Collyer, who earlier ordered a more extensive environmental study of the project because of the Manitoba lawsuit. That study was finished last year, with the federal government recommending a $17.5 million water treatment plan that involves using chemicals and ultraviolet disinfection at a plant to be built between Minot and Lake Sakakawea in northwest North Dakota.

While the study was being done, the judge allowed only construction unrelated to water treatment - such as the laying of pipeline - to continue.

State officials are now eager to begin work on the water treatment part of the project, but Collyer must first decide whether the government's treatment plan satisfies her order for a more complete environmental review. She also must consider Missouri's complaints.

North Dakota officials had hoped the judge would address both matters by the end of the year. Klose said the delay in filing briefs will push back other filing deadlines, to late October.

"Then we're expecting the court to ask for a hearing, for oral arguments … and then we're getting into the holiday season," Klose said. "It's getting a little bit iffier" that the lawsuits will be resolved by the end of the year, she said.