Environmental groups are suing the State Department to halt the 1,980-mile Keystone oil pipeline, saying the government did not fully investigate the risks of leaks and other damage to rural areas.

The lawsuit was filed this week in Washington, D.C., by the New York-based Natural Resources Defense Council, Inc., the Dakota Resource Council of Dickinson and Dakota Rural Action of Brookings, S.D. It seeks to halt the project until the environmental impacts of the pipeline are addressed.

The State Department issued a permit allowing Alberta-based TransCanada Corp., to build the pipeline, from Hardisty, Alberta to Midwestern refineries.

State Department spokeswoman Nichole Thompson said Friday the agency does not comment on ongoing legal action. Pipeline representatives did not return a message seeking comment.

TransCanada and Houston-based ConocoPhillips are partners in developing the pipeline. The first phase of construction has started in North Dakota and South Dakota, and the developers hope to start delivering oil next year.

The lawsuit says the project will lead to "increased air and water pollution for residents of the Midwest and other states." It says the pipeline will supply refineries with extra heavy sour crude oil extracted from Canadian tar sands could release more greenhouse gases and other pollution.

In May, South Central District Judge Gail Hagerty dismissed pipeline opponents' request to delay construction in North Dakota, saying they were not likely to win their arguments that the route was too close to drinking water sources. The state Public Service Commission had imposed almost three dozen conditions for construction and ordered the company to pay for an inspector.

In a statement announcing the lawsuit, the resource groups said landowners in North Dakota and South Dakota continue to fight pipeline siting and eminent domain proceedings but find themselves "outgunned by TransCanada's resources."

"To extract this low quality oil from tar sands, oil companies are burning through reserves of natural gas our children will need one day," the statement said. "Dredging up dirtier and dirtier oil to fuel inefficient vehicles is like washing the dishes with scotch, and the damage to our rural way of life keeps mounting."