A nearly-complete $2.3 billion pipeline to carry natural gas from West Texas shale fields to the U.S. Gulf Coast can move ahead, a U.S. judge in Austin, Texas, ruled on Friday, rejecting an environmental group's effort to halt the project.

Sierra Club in April challenged federal approval of the 428-mile (689 km) Kinder Morgan Inc pipeline, alleging regulators' reviews under a streamlined process were faulty. The line's path crosses areas with two endangered species and some 400 wetlands, lawyers wrote.

The U.S. Army Corps of Engineers, which issued permits for the Permian Highway pipeline, said no further reviews are needed.

The project is 90% mechanically complete and could begin operation in early 2021. "We look forward to completion of this vital energy infrastructure project," Kinder Morgan spokeswoman Katherine Hill said in a statement.

"We are disappointed that the court declined to put an immediate stop to this illegal construction, and we are evaluating our options," said Sierra Club attorney Joshua Smith.

Legal challenges have delayed the Dakota Access, Keystone XL, and Trans Mountain oil pipelines, and led to a cancellation of the Atlantic Coast natural gas pipeline.

The proposed Kinder Morgan line would bring 2.1 billion cubic feet per day of natural gas from West Texas to the Gulf Coast.

U.S. District Court for Western District of Texas Judge Robert Pitman denied the request for a preliminary injunction, saying the group did not show that continued construction would cause irreparable harm to landowners or endangered species.

"Unfortunately, granting an injunction at this state of the pipeline's completion would not 'unring the bell,'" he wrote in his decision, adding that the Sierra Club "failed to establish a definitive threat of future harm."

The pipeline is owned by Kinder Morgan, Exxon Mobil, Altus Midstream and Blackstone Group's EagleClaw Midstream Ventures.

(Reporting by Gary McWilliams; Editing by Paul Simao) ((Gary.McWilliams@thomsonreuters.com; +1 713-210-8513;))