In a three-page letter sent to congressional leaders, Rosselló is requesting more than $4 billion from various agencies and loan program to "meet the immediate emergency needs of Puerto Rico."
"We are grateful for the federal emergency assistance that has been provided so far," Rosello wrote. "However, absent extraordinary measures to address the halt in economic activity in Puerto Rico, the humanitarian crisis will deepen, and the unmet basic needs of the American citizens of Puerto Rico will become even greater."
The Trump administration submitted a $29 billion disaster relief request to Congress last week to cover ongoing relief and recovery efforts in the wake of hurricanes Harvey, Maria and Irma, and to pay federal flood insurance claims. The House is expected to vote on that measure as soon as this week.
But the administration has also been conducting its own review of Puerto Rico's precarious financial position, sources involved with the process said, with the expectation that additional help will be necessary in the near future. The question of how soon that additional aid will be needed has been the subject of debate, the sources said.
With the letter, Rosselló, who congressional aides said has spent much of the last week phoning key lawmakers to urge action, made clear that, at least in his view, the additional action needs to be taken immediately.
"Financial damages of this magnitude will subject Puerto Rico's central government, its instrumentalities, and municipal governments to unsustainable cash shortfalls," Rosselló wrote. "As a result, in addition to the immediate humanitarian crisis, Puerto Rico is on the brink of a massive liquidity crisis that will intensify in the immediate future."
Rosselló also pointed to a potential exodus of the island's inhabitants should aid not be available in a timely manner -- something he has also emphasized in conversations with lawmakers.
"This could lead to an acceleration of the high pace of outmigration of Puerto Rico residents to the U.S. mainland impacting a large number of states as diverse as Florida, Pennsylvania, New Hampshire, Indiana, Wisconsin, Ohio, Texas, and beyond," Rosselló wrote.