US President Donald Trump has approved a disaster declaration for Puerto Rico after Hurricane Maria slammed into the US territory, with fears it could be without power for months.
The strongest hurricane to hit Puerto Rico in over 80 years destroyed hundreds of homes, knocked out power across the entire island and triggered heavy flooding.
The declaration makes federal funding available to Puerto Ricans affected by the storm.
Mr Trump also said he would visit the island territory during the media briefing.
The extent of the damage is unknown given that dozens of municipalities remained isolated and without communication after Maria blew ashore on Wednesday morning in the south-east coastal town of Yabucoa as a Category 4 storm with winds of 155mph.
Uprooted trees and widespread flooding blocked many roads across the island, creating a maze that forced drivers to go against traffic and past police cars that used loudspeakers to warn people they must respect a curfew imposed by the governor to ensure everyone's safety.
Puerto Rico's electric grid was crumbling amid lack of maintenance and a dwindling staff even before the hurricanes knocked out power. Many now believe it will take weeks, if not months, to restore power.
The now-Category 3 hurricane is centered about 95 miles north-northwest of Punta Cana, Dominican Republic, and is moving northwest at 9 mph and is expected to pass near the Turks and Coacos later today.
"Once we're able to go outside, we're going to find our island destroyed," Puerto Rico's emergency management director Abner Gomez said.
"The information we have received is not encouraging. It's a system that has destroyed everything in its path."
It was the second time in two weeks that Puerto Rico felt the wrath of a hurricane.
Hurricane Irma sideswiped Puerto Rico on September 6, leaving more than one million people without power but causing no deaths or widespread damage like it did on nearby islands.
There has been one reported death, with Puerto Rico's governor saying one man died after being hit by flying debris.
At least 10 deaths have been recorded across the Caribbean, including seven in the hard-hit island of Dominica and two in the French Caribbean territory of Guadeloupe.
Puerto Rico had long been spared from a direct hit by hurricanes that tend to veer north or south of the island.
The last Category 4 hurricane landfall in Puerto Rico occurred in 1932, and the strongest storm to ever hit the island was San Felipe in 1928 with winds of 160mph.
The storm also blew over the tiny eastern Caribbean island of Dominica late Monday, where Prime Minister Roosevelt Skerrit sent out a series of dramatic posts on his Facebook page, including that his own roof had blown away.
"The winds are merciless! We shall survive by the grace of God," Mr Skerrit wrote before communications went down.
Maria is the third Category 4 hurricane to make landfall in the United States during the 2017 Atlantic hurricane season, after Harvey and Irma.
This is the first time three Category 4 hurricanes have made landfall in the US in the same season since records began in 1851.