The law known as the Jones Act limits the number of ships that could be sent to Puerto Rico, a USA territory, and thus the amount of relief supplies that have come in since the hurricane.
In a statement about the issues, the FDA says, "We are aware of several other instances where we may soon face critical shortages if we don't find a path for removal or ways to get production back up and running".
Between calls to boycott the National Football League and to support repeal of the Affordable Care Act, Trump's few tweets and retweets about the disaster in Puerto Rico have been vague and largely self-congratulatory.
During a briefing, Congresswoman Nydia Velazquez (D-NY) said she found the conditions "shocking" when she visited the island on Friday. "Food and water on site", he wrote.
Donald Trump has announced he will allow foreign owned ships to deliver relief supplies from USA ports to Puerto Rico following a furore over his previous comments that it would upset American shipping firms.More news: Michelle In Talks To Join Tom Hardy, Riz Ahmed In 'Venom'
In Washington, some politicians said the Jones Act waiver should last longer or that the law should be completely repealed.
Scott spoke by phone on Wednesday with both Rosselló and Puerto Rico Congresswoman Jennifer González-Colón, as well as directors at Port Everglades, PortMiami and Port Canaveral.
One resident, Juan Cruz, told Reuters news agency as he filled a container from a water tanker: "We can use more help". Critics have called the act anachronistic and argue that it is stalling recovery efforts in the badly damaged island territory that was hit by two massive storms in quick succession this month. Meanwhile, area clergy urged Scott to lobby federal officials to lift restrictions on religious groups being able to help deliver urgently needed relief supplies.
The island, located 1,150 miles off the southeastern coast of Florida, remains largely under blackout.
Most of the Caribbean island's 3.4 million people also are without electricity.
"We've got to just keep being creative and thinking, OK, so what are the needs?"