Donald Trump has finally responded to the devastation wrought in Puerto Rico, five days after Hurricane Maria slammed into the US territory.

But the President's words offered little comfort to the Caribbean island's 3.4 million American citizens, describing Puerto Rico as "in deep trouble" and criticising its "broken infrastructure and massive debt".

At least 16 people are dead and the entire island's power network remains down after the worst storm in nearly a century hit the island last week.

Mr Trump told Puerto Ricans through Twitter "we are with you" before the hurricane struck on September 20 but for days said nothing about the disaster left in its wake. The President was not, however, absent on social media during this time, instead using the platform to criticise NFL players kneeling in protest of racial inequality.

He broke his silence on Puerto Rico with a series of posts that acknowledged "much of the island was destroyed" but derisively noted parts of its infrastructure were already "in terrible shape".

"Texas and Florida are doing great but Puerto Rico, which was already suffering from broken infrastructure and massive debt, is in deep trouble," he wrote.

"It's [sic] old electrical grid, which was in terrible shape, was devastated. Much of the Island was destroyed, with billions of dollars owed to Wall Street and the banks which, sadly, must be dealt with. Food, water and medical are top priorities - and doing well."

The President did not offer a solution for dealing with Puerto Rico's $72bn (£53bn) debt. The US territory filed the biggest government bankruptcy in American history earlier this year.

On Monday Puerto Rico's government asked a judge for up to four extra weeks to meet key deadlines in its bankruptcy case, after Maria's 140mph winds and torrential rain brought its fragile infrastructure to its knees.

Puerto Rico Governor Ricardo Rossello also pleaded for more government aid to avert a humanitarian crisis in the island, where drinking water and food supplies remained scarce this week.

Many of the country’s hospitals are dependent on diesel generators and the injured have been flown to the US for treatment.

A man looks at the damage after his house was hit by Hurricane Maria in Toa Baja, Puerto Rico (REUTERS)

The White House has faced criticism that its response to Hurricane Maria failed to match support given to Texas and Florida after the recent hurricanes which lashed the two states.

Spokeswoman Sarah Sanders told reporters in Washington the administration was engaged in a fact-finding process to work out how much help Puerto Rico needs.

The Trump administration ruled out temporarily setting aside federal restrictions on foreign ships' transportation of cargo, saying it was not necessary and that supplies could be carried more efficiently by air. The government had waived those rules in Florida and Texas until last week.

The US has deployed 4,000 US Army Reserve members to Puerto Rico, as well as 1,600 National Guard members, according to the Federal Emergency Management Agency.

Puerto Rico is an unincorporated US territory, meaning its inhabitants have qualified US citizenship, and it is entitled to federal emergency funds.

Democratic politicians with large Puerto Rican constituencies in mainland US said the response was too little and too slow.

"Puerto Ricans are Americans," said Representative Nydia Velazquez, who travelled to Puerto Rico over the weekend to assess the damage. "We cannot and will not turn our backs on them."

Mr Trump himself was expected at the end of last week to visit Puerto Rico and the US Virgin Islands, after they had been ravaged by Hurricane Irma. But the trip was delayed after Maria set its sights on the islands.