Image copyright AFP Image caption A householder in the storm-hit ruins of her home in Aibonito, Puerto Rico

US President Donald Trump has griped about emergency relief efforts in hurricane-ravaged Puerto Rico, saying federal aid cannot continue "forever".

In tweets, he accused Puerto Rico of a "total lack of accountability", adding that "electric and all infrastructure was disaster before hurricanes".

The island, whose 3.4 million residents are US citizens, is 90% without power, some three weeks after Hurricane Maria.

On Thursday, Congress approved a $36.5bn (£28bn) disaster relief bill.

The cross-party bill, which still requires Senate approval, provides emergency storm relief for Puerto Rico, Florida, Texas and the US Virgin Islands, as well as wildfire-ravaged California.

In Thursday's morning tweets, the US president noted it was up to "Congress to decide how much to spend".

But he added: "We cannot keep FEMA, the Military & the First Responders, who have been amazing (under the most difficult circumstances) in P.R. forever!"

Skip Twitter post by @realDonaldTrump "Puerto Rico survived the Hurricanes, now a financial crisis looms largely of their own making." says Sharyl Attkisson. A total lack of..... — Donald J. Trump (@realDonaldTrump) October 12, 2017 Report

Skip Twitter post 2 by @realDonaldTrump ...accountability say the Governor. Electric and all infrastructure was disaster before hurricanes. Congress to decide how much to spend.... — Donald J. Trump (@realDonaldTrump) October 12, 2017 Report

The mayor of Puerto Rican capital San Juan said Mr Trump's tweets highlight his "desperation" and the "inadequacy" of the hurricane response.

"It is not that you do not get it," Carmen Yulin Cruz added, "it is that you are incapable of empathy and frankly simply cannot get the job done."

White House chief of staff John Kelly said later the US would stand with Puerto Rico "until the job is done".

He also said the president was "exactly accurate" to assert that federal personnel are "not going to be there forever".

Media playback is unsupported on your device Media caption John Kelly: 'I was not brought in to control Trump'

The storm killed at least 45 people in the US territory, while more than 100 others remain unaccounted for, say Puerto Rico officials.

The island is saddled with about $72bn in pre-hurricane debt that is being overseen by a federally created oversight board.

Chequebook comes out, empathy ends

Analysis by Anthony Zurcher, BBC North America reporter

Imagine a devastating hurricane hits New York City, and the president repeatedly notes how bad things were there before the disaster. Or, three weeks after an earthquake levels Los Angeles, he says the government won't provide aid "forever".

There would be outrage. It's difficult to even imagine such responses.

That, however, is how Donald Trump is handling hurricane-ravaged Puerto Rico. For the president, the US territory - occupying a political no-man's land between US statehood and independence - is different.

When the chequebook comes out, empathy ends and reality sets in. The administration and Congress are in the middle of tough negotiations over government spending and tax reform. Coming up with billions for Puerto Rico relief is an unwelcome challenge.

So the president has said there is a limit to the help available for these taxpaying US citizens. Things were bad before - and they may stay that way.

Mr Trump's tweets also provoked a backlash from some Democratic lawmakers, who accused him of preparing to abandon US citizens.

"There is still devastation, Americans are still dying. FEMA needs to stay until the job is done," Senate Democratic Leader Chuck Schumer replied on Twitter, using the acronym for the Federal Emergency Management Agency.

Puerto Rico-born congresswoman Nydia Velazquez, another New York Democrat, tweeted that Mr Trump's comments were "outrageous, indefensible and irresponsible", adding: "We will not allow our government to abandon our fellow citizens."

Image copyright Getty Images Image caption Interior roads are very damaged, as authorities prioritise mending coastal roads

She has written to the Department of Homeland Security to request an investigation into the official death toll, which she says may be vastly under-reported, and could be as high as 450.

"The federal response is woefully adequate and now we are seeing numerous reports that the death toll is unknown or not being reported accurately," she wrote in a letter co-authored with Congressman Bennie Thompson of Mississippi.

"The whole nation deserves to know what is happening to our fellow citizens."

President Trump visited the US territory last week, where he told residents that recovery efforts had "thrown our budget a little out of whack".

Media playback is unsupported on your device Media caption The Quinones family show the BBC what's left of their home

He also said the islanders should be "very proud" the death toll was not as high as a "real catastrophe" like Hurricane Katrina, which devastated New Orleans in 2005.

The US president was pilloried by local officials after he threw rolls of paper towels at residents during his trip.

The San Juan mayor described that incident as "abominable".

But Mr Trump later depicted the outrage as confected, insisting to the Trinity Broadcasting Network that the crowd "were having fun" as he distributed "these beautiful, soft towels".