Story highlights Puerto Rico governor: "Absent extraordinary measures ... the humanitarian crisis will deepen"

Relief and recovery efforts are ongoing in Puerto Rico in the wake of hurricanes Harvey, Maria and Irma

(CNN) Puerto Rico Gov. Ricardo Rosselló, citing an "unprecedented catastrophe," is lobbying Capitol Hill for a significant new influx of money in the near term as the island sits on the brink of "a massive liquidity crisis," according to a letter obtained by CNN.

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.

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