Senator Joe Manchin III of West Virginia has secured a promise from Democratic leaders and the White House to complete a highly contested 304-mile gas pipeline in his state, his office said, a major concession won as part of negotiations over a climate and tax bill…

It would ensure that federal agencies “take all necessary actions to permit the construction and operation” of the gas line, known as the Mountain Valley Pipeline. The project — which has been opposed for years by environmentalists, civil rights activists and many Democratic state lawmakers in Virginia — would carry natural gas from the Marcellus shale fields in West Virginia across nearly 1,000 streams and wetlands before ending in Virginia.

The pipeline was originally supposed to be completed by 2018 but environmental groups have successfully challenged a series of federal permits for the project in the United States Court of Appeals for the Fourth District in Richmond, Va.