U.S. President Donald Trump’s administration on Monday extended a Jones Act waiver by 90 days while narrowing its scope, keeping fewer U.S. shipping restrictions in place during the war with Iran to maintain fuel supplies. According to Sina Finance, a White House official said the latest extension applies only to vessels carrying certain energy resources and also requires the Pentagon to consult with the U.S. Maritime Administration to determine whether the waiver applies to each individual shipping voyage.

The official said the added restrictions were in response to concerns from the U.S. maritime industry. The Jones Act is a 1920 law that requires cargo transport between U.S. ports to be carried by U.S. ships.

According to U.S. Maritime Administration data cited by the Cato Institute, 210 voyages have been completed since Trump first granted the waiver, and the waivers have carried nearly 55 million barrels of cargo.