A federal judge has ordered North Dakota to stop construction on part of a $2 billion flood control project along the Red River — a project Minnesota hasn't signed off on yet.

U.S. District Judge John Tunheim issued a temporary injunction on Wednesday to halt the construction of a $70 million ring levee around three small North Dakota towns just south of flood-prone Fargo.

Diversion opponents argued that North Dakota shouldn't start building until Minnesota gives its blessing. Part of the $1.8 billion Fargo-Moorhead Diversion plan includes stretching a dam across the Red River — a dam that would keep Fargo dry by backing floodwaters onto stretches of Minnesota and North Dakota instead.

The Minnesota Department of Natural Resources is conducting a detailed environmental review, and had asked North Dakota to hold off on construction until that review is complete in August. But North Dakota broke ground last summer, countering that it should be free to build on its own land, using its own money.

On Wednesday, the federal judge sided with Minnesota, which had joined the ongoing lawsuit against the project as a friend of the court. The public costs of delaying construction "are relatively minor," Tunheim wrote, compared to the risk of running roughshod over Minnesota's environmental review process.

"The law simply requires that all federal and state environmental reviews be completed before construction begins," Tunheim wrote. "Construction of the … ring levee violates this principle and creates the real risk of a 'steam roller' effect."

DNR Commissioner Tom Landwehr welcomed the ruling. When the draft report comes out at the end of summer, it will be followed by a public comment period before Landwehr determines whether Minnesota will grant the permits to allow the diversion project to move forward.

"It's a very complicated project that has lots of benefits and impacts," he said. "We just have to take the time that we need to think it through, take a hard look, make sure we get it right. That's all we're asking for."

The current plans for the Red River diversion call for a 36-mile channel around Fargo to steer floodwater around the city, instead of over it.