He tweeted: "We can not keep FEMA, the Military & the First Responders, who have been fantastic (under the most hard circumstances) in P.R. forever!"
Maria slammed into Puerto Rico as the island was already struggling with a severe financial crisis, which forced the government to file for bankruptcy in May.
Rep. Scott Perry, R-Pennsylvania, who is a member of the House foreign affairs committee, told CNN's Chris Cuomo Thursday there's only "so much" the U.S. can do to help Puerto Rico.
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Both Trump and Vice President Mike Pence visited the island last week to offer the USA commitment to the island's recovery.
Rossello said he has asked Trump for an additional US$4.9 billion under the Community Disaster Loan program.
Carmen Yulin Cruz, mayor of the island's capital San Juan who has publicly feuded with Trump in recent weeks, pushed back hard at the president's apparent threat to withdraw federal aid, charging that he was incapable of "fulfilling the moral imperative to help" Puerto Ricans. "We will not allow the federal government to abandon Puerto Rico in its time of need". It knocked out electricity to the whole island and caused widespread damage to homes and infrastructure.
Trump's remarks on Thursday cap those he said while visiting the island on October 3 when he said Puerto Rico's hurricane wasn't a "real catastrophe" like Hurricane Katrina and that response to relief efforts were "throwing our budget a little out of whack".
Democrats said Trump's attacks were "shameful", given that the 3 million-plus US citizens on Puerto Rico are confronting the kind of hardships that would draw howls of outrage if they affected a state.
"He wrote in two separate tweets, "'Puerto Rico survived the Hurricanes, now a financial crisis looms largely of their own making.' says Sharyl Attkisson. By suggesting he might abdicate this responsibility for our fellow citizens in Puerto Rico, Mr. Trump has called into question his ability to lead.
The legislative aid package totals $36.5 billion and sticks close to a White House request.
More than a dozen years after Hurricane Katrina pounded the Gulf Coast, FEMA was slated to dole out almost half a billion dollars in fiscal year 2017 to fund relief efforts, mostly in Louisiana, after the hurricane and subsequent storms Rita and Wilma.
Up to $5 billion of the FEMA money could be used to help local governments remain functional as they endure unsustainable cash shortfalls in the aftermath of Maria, which has choked off revenues and strained resources. He has promised that the island will get what it needs. Authorities told CNN on Wednesday that the death toll had gone up to 45, but at least some 113 people were still unaccounted for.