US President Donald Trump on Saturday placed blame squarely on Puerto Ricans for the slow recovery from Hurricane Maria after critics and the mayor of San Juan complained his administration's response to the US territory's plight was insufficient.

Eleven days after the devastating storm wiped out power, water and communications systems, about half of the 3.4 million people on the island do not have access to drinking water, and 95 percent remain without power, according to the U.S. Defense Department.

"I'm a ticking time bomb on the verge of exploding," said Adeline Vazquez, 53, who needs a ventilator for respiratory problems and whose building in the western city of Mayaguez does not have enough fuel to run a generator 24 hours a day.

Maria, the most powerful storm to strike Puerto Rico in nearly 90 years, has destroyed roads, making it difficult to deliver aid and move the heavy equipment needed to fix damaged infrastructure across the island. The hurricane has killed at least 16 people, according to the official death toll.

Trump, who plans to visit the island on Tuesday, fired off a series of angry tweets from his private golf club in New Jersey, taking aim at the mayor of San Juan, the island's capital and largest city.

On Friday, Carmen Yulin Cruz criticized Trump's administration and begged for more help, a plea that received widespread television coverage in the mainland United States.

"Such poor leadership by the Mayor of San Juan and others in Puerto Rico who are not able to get their workers to help," said Trump, a Republican. "They want everything to be done for them when it should be a community effort."

Trump - who often turns to Twitter to strike out when his government is under pressure - accused Cruz of being "told by the Democrats that you must be nasty to Trump" and blamed the media for not showing the "amazing job" of responders.

Cruz, who has been living in a shelter after her home was destroyed in the hurricane, said municipal employees were working as hard as they could. She also said her complaints had resulted in more food and water being provided.

Cruz responded to Trump's attack by saying she had no time for petty politics when lives were at stake.

"Sometimes you have to shake the tree in order to make things happen," she told the New York Times. "And if that has a political cost, I will take it, as long as it saves lives."

The heated rhetoric took the political tensions around the disaster to new heights, but Puerto Rico Governor Ricardo Rossello tried to distance himself from the battle ahead of Trump's visit.

In an interview with Reuters on Saturday, Rossello said: "I'm not paying attention to social media," adding "my only focus right now is to make sure the people of Puerto Rico are well."

When pressed, Rossello said he did not interpret Trump's tweets as a slight to Puerto Rico's people.

"When I read that tweet, it was in reference to the mayor of San Juan, not to the people of Puerto Rico," said Rossello, who has made a point of working cooperatively with Trump's administration on aid for the island.

"I saw it as a personal difference with the mayor of San Juan," he said.

Rossello and Cruz are members of rival political parties.

But Trump's comments drew swift condemnation elsewhere, particularly from US Democrats.