US President Donald Trump has lifted shipping restrictions to help fuel and supplies reach storm-ravaged Puerto Rico, the White House has said.
Mr Trump “has authorized the Jones Act be waived for Puerto Rico”, a statement said on Twitter.
Puerto Rico had pressed the US to lift the act, which limits shipping between coasts to US-flagged vessels.
The US territory is struggling with fuel, water and medical shortages one week after Hurricane Maria struck.
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The most powerful hurricane to hit Puerto Rico in nearly 90 years, Maria swept across the island last Wednesday.
How bad is the situation on Puerto Rico?
Many of its 3.4 million residents have been without electricity, reliable drinking supplies and other basic necessities since the storm struck.
The death toll was not as bad as the scores killed by Hurricane Irma – Maria claimed more than 30 lives in the Caribbean, including at least 16 in Puerto Rico.
But Maria knocked out the US territory’s entire power grid, crippling its water and sewage treatment system.
More than 90% of cellular communication sites remain out of service, US officials say.
Puerto Rico, which gets most of its fuel by ship from the US, has been under petrol rationing since the hurricane struck.
Service stations have been able to stay open only a few hours at a time, while most hospitals lack power or fuel for their electrical generators.
Residents have been queuing for hours to get diesel fuel to power generators, and some have mobbed water-supply tankers.
One resident, Juan Cruz, told Reuters news agency as he filled a container from a water tanker: “We can use more help. We are US citizens. We are supposed to be treated equally.”
Ricardo Rossello, the island’s governor, has called its devastation an unprecedented natural disaster.
How is the US responding?
Federal emergency management officials and the US military have stepped up relief efforts as the scale of the island’s crisis has become clear.
The Federal Emergency Management Authority said it had delivered more than 4.4m meals and 6.5m litres of water to Puerto Rico and the US Virgin Islands by Wednesday.
But the transport of relief supplies has been hampered by roads rendered impassable by fallen trees or flooding.
The 1,000-bed US Navy hospital ship Comfort will arrive next week, after sailing from its home port in Virginia on Friday.
President Trump was criticised for spending the weekend focusing on a feud with NFL players and coaches, instead of the Puerto Rico disaster.
What is the Jones Act?
By waiving the Jones Act, the US will allow for more rapid delivery of aid to Puerto Rico.
The legislation, known formally as the Merchant Marine Act of 1920, requires goods ferried to US ports to be sent on ships that are built, owned and operated by Americans.
The regulation was created to promote the American commercial shipping industry.
But it has made the price of goods in Puerto Rico more expensive than those on the US mainland or other Caribbean islands.
The cost of living in Puerto Rico is also higher as a result.
Foreign goods must first be sent to the US mainland and transferred to American ships before they can be sent to US territories such as Puerto Rico.
This means aid from countries such as the nearby Dominican Republic cannot directly be sent to the devastated island.
The US waived the Jones Act during the recent Hurricanes Harvey and Irma to help ships quickly reach Texas and Florida.
Note: This story is auto-generated from BBC syndicated feed and has not been edited by AFRICA PRIME NEWS