More than 15 people are dead and 20 remain missing after Hurricane Maria's direct hit on Dominica, the prime minister has said.
Roosevelt Skerrit cried as he spoke to a reporter on the nearby island of Antigua.
He said more than 15 people died because of the storm and that it was a miracle that the death toll was not in the hundreds.
The centre of the Category 4 storm hit Dominica with massive force late Monday night and early Tuesday, destroying hundreds of homes and cutting off the mountainous island's communication systems and shutting its airport.
Mr Skerrit said Dominica "is going to need all the help the world has to offer".
Meanwhile, the US Coast Guard, US Navy and the Royal Navy are searching for a boat that went missing off Puerto Rico during the hurricane, with two adults and two children aboard.
The coastguard in Miami said the Ferrel sent a distress call on Wednesday saying it was disabled and adrift in seas with 20ft waves and 100mph winds.
Communications were lost with the boat near Vieques, Puerto Rico.
The search includes an HC-130 plane, a fast response cutter, the USS Kearsage amphibious assault ship and navy helicopters.
Rescuers have fanned out to reach stunned victims after Maria ravaged Puerto Rico, knocking out electricity to the entire island and triggering landslides and floods.
The extent of the damage is unknown given that dozens of districts remained isolated and without communication after Maria hit the island on Wednesday morning with 155mph winds, the strongest hurricane to hit Puerto Rico in more than 80 years.
Uprooted trees and widespread flooding blocked many highways and streets across the island of 3.4 million, creating a maze that forced drivers to go against traffic and past police cars that used loudspeakers to warn people they must respect a 6pm to 6am curfew imposed by the governor.
People resorted to rafts and kayaks to get around because flooding made many roads remained impassable.
"This is going to be a historic event for Puerto Rico," said Abner Gomez, the island's emergency management director.
US president Donald Trump approved a federal disaster declaration for Puerto Rico.
Previously a Category 5 with 175mph winds, Maria hit Puerto Rico as the third-strongest storm to make landfall in the US, based on its central pressure.
It was even stronger than Hurricane Irma when that storm roared into the Florida Keys earlier this month.
In the capital of San Juan, towering eucalyptus trees fell nearly every other street over a main road dotted with popular bars, restaurants, and coffee shops, some of which were damaged.
Hurricane Irma sideswiped Puerto Rico on September 6, leaving more than one million people without power but causing no deaths or widespread damage.
Maria, however, blew out windows at some hospitals and police stations, turned some streets into roaring rivers and destroyed hundreds of homes across Puerto Rico, including 80% of houses in a small fishing community near the San Juan Bay, which unleashed a storm surge of more than four feet.
"Months and months and months and months are going to pass before we can recover from this," Felix Delgado, mayor of the northern coastal city of Catano, said.