"I am very concerned by the Department's decision not to waive the Jones Act for current relief efforts in Puerto Rico, which is facing a worsening humanitarian crisis following Hurricane Maria", he wrote in the letter.
For people who have family and friends still on the island, Dunn urges them to not give up hope. "This is 3.1 or 2 million Americans that are without power, without running water".
On the island, 44 percent of the people don't have access to clean drinking water.
Other videos showed damaged buildings and uprooted trees.
During a press conference held on Tuesday, President Trump defended the administration's handling of the situation by pointing out that Puerto Rico is an island and that the government can't just "drive your trucks there from other states".
Agriculture, once the backbone of the Puerto Rican economy, took a direct hit.
"They need water, gas for their generators, and food". The Jones Act requires ships that deliver goods between American ports to be American-built, which isn't a big deal for most Americans.
It is hard to avoid the fact that the response looks different than previous ones.
A powerful hurricane rips through an island and you haven't heard from your loved ones who live there in a week.
In a Facebook post today, Mark Zuckerberg pledged $1.5 million in aid to organizations assisting in Puerto Rico's recovery from Hurricane Maria, together with direct assistance from Facebook's connectivity team to help the country get back online.
"There's a lot of good faith, but the good faith has to turn into action or people are going to continue to die", Cruz said.