Final approval of hundreds of interstate pipelines, transmission lines and liquefied-natural-gas projects will be delayed for months because the Trump administration has changed leadership at the Federal Energy Regulatory Commission. That move leaves FERC one short of the three-member quorum needed to vote on energy projects.

President Donald Trump on Jan. 26 elevated FERC Commissioner Cheryl LaFleur, a Democrat and former electricity industry executive, to acting chairman. The same day, Chairman Norman Bay announced that he would step down from the commission on Feb. 3.

That leaves the FERC—responsible for regulating and approving interstate gas pipelines, hydropower facilities and LNG terminals —with just LaFleur and Commissioner Colette Honorable, a Democrat. The five-member panel has operated with just three members since September.

Much of FERC’s work, such as environmental reviews, can continue. But final approval of major projects requires three members. Projects awaiting final approval include three pipelines—the NEXUS gas transmission project and the Atlantic Sunrise and Rover pipelines—that would take natural gas from the Marcellus region to markets.

To reach a quorum, the Trump administration will have to nominate at least one Republican commissioner who can win Senate approval. That process probably will take months, said Andy Byers, Black & Veatch associate vice president and environmental director.

William S. Scherman, partner at the law firm Gibson, Dunn & Crutcher and a former FERC general counsel, said he expects that FERC will soon issue an order delegating more authority to its staff.

Byers said it is possible that Trump could grant FERC emergency authority to approve projects; however, in the past, such powers have been used only in situations involving national security.

Industry groups, including the Interstate Natural Gas Association of America, and key lawmakers, such as Senate Energy and Natural Resources Committee Chairman Lisa Murkowski (R-Alaska), are urging the administration to act quickly to nominate candidates to fill the FERC’s open slots.