The US military and all relevant agencies are under orders to do "everything in their power" to help Puerto Rico, US President Donald Trump said on Tuesday.

Read more: Puerto Rico officials weigh devastation

Addressing the reporters in Washington DC, Trump rejected the accusations that his administration was slow to provide hurricane relief for the predominantly Hispanic US territory. Some observers had claimed that the government has been far less efficient in Puerto Rico compared to its recent aid drives in Texas and Florida.

"We've gotten A-pluses on Texas and in Florida, and we will also on Puerto Rico," Trump said. "The difference is this is an island sitting in the middle of an ocean. It's a big ocean; it's a very big ocean. And we're doing a really good job."

No power, no water

Hurricane Maria has claimed at least 16 lives since hitting the US territory less than a week ago, in a region already shaken by Hurricane Irma earlier this month. Large parts of the island, including most of its hospitals, are still without power, and almost one half of 3.4 million residents of Puerto Rico have no access to clean water. The Puerto Rico governor asked for urgent federal aid to deal with "unprecedented" destruction.

On Tuesday, Trump promised to visit the island next week. The White House also pledged to pay 100 percent of the costs for debris removal and other emergency assistance to Puerto Rico, instead of the usual 75 percent.

US military to deploy more troops

The Pentagon, which has troops working on disaster relief in Texas and Florida, promised to boost the number of troops in Puerto Rico from the current 2,500 to as many as 5,000 in the next several days. The United States currently has 16 Navy and Coast Guard ships operating near Puerto Rico and 10 more are on the way, said Federal Emergency Management Agency (FEMA) Administrator Brock Long. One of those vessels is USS Comfort, a Navy hospital ship.

"We're dramatically increasing the federal footprint that's there," Long said, speaking outside the White House.

Read more: Puerto Rico evacuates thousands as dam breach threatens floods

The storms dealt heavy damage to airports and seaports, posing logistical challenges for the relief teams, Long told reporters. Military aircraft were dropping food and water to the parts of the island that are still cut-off, he added. The destruction was particularly severe due to poor infrastructure on the impoverished US territory.

"Unfortunately, because of the severity of the hit, there is diminished capacity of local governments and state government to respond similar to what we saw with Texas and Florida," Long said.

Officials estimate it will take over a month to fix the islands severely damaged power grid and restore power to all of its inhabitants.

dj/sms (AP, AFP, Reuters)