President Donald Trump is seriously considering waiving the requirement that only U.S.-flagged vessels can move natural gas from American ports to Puerto Rico or the Northeast, according to people familiar with the deliberations. The issue was debated during an Oval Office meeting on Monday, following requests from Puerto Rico and pressure from oil industry leaders to ease the nearly 100-year-old Jones Act requirements, according to three people. Although top administration officials are divided on the issue, Trump is now leaning in favor of some kind of waiver, said two of the people, who asked for anonymity to discuss the private deliberations.

The move — which would be fought by U.S shipbuilding interests and their allies on Capitol Hill — has been promoted as essential to lower the cost of energy in Puerto Rico and ease the flow of American natural gas to the U.S. Northeast, where there aren’t enough pipelines to deliver the product from Pennsylvania.  But even inside the Trump administration, there are fierce defenders of the Jones Act, a 1920 law requiring that vessels moving cargo between two U.S. ports be U.S.-built, -owned and -crewed. The law was originally designed to protect the domestic shipping industry and the country’s maritime might, and supporters argue that it’s just as essential today to ensure ships are made in the U.S. Any move to weaken or waive the requirements threatens the U.S. shipbuilding industry and the jobs tied to it, they argue.