US President Donald Trump and first lady Melania Trump meet with first responders and private citizens who helped during the mass shooting, during an event at the Las Vegas Police Command Center on Wednesday. [Photo/Agencies]

During Tuesday's trip, he highlighted Puerto Rico's relatively low death toll compared with "a real catastrophe like Katrina," when as many as 1,800 people died in 2005 as levees protecting New Orleans broke. He also pointed repeatedly to praise his administration had received for its efforts, despite criticism on the island of a sluggish response.

Trump has a long personal connection to Las Vegas — a city where his name is written in huge golden letters atop his hotel. He also campaigned extensively across Nevada during his presidential campaign, drawing large crowds to rallies along the Las Vegas strip.

Trump told reporters Tuesday night that his trip would include spending time with "some of the folks that are recovering, some of the survivors", and seemed emotional as he spoke about the human toll.

"We're going to be seeing — ah it's a very, it's very, it's a very — horrible thing, even to think about. Really horrible," he said. "We're also meeting with the police, the sheriff, and we're going to spend quite a lot of time in Las Vegas."

Trump was also joined on the trip by House Majority Leader Kevin McCarthy and Nevada Republicans Representative Mark Amodei and Senator Dean Heller.

Trump offered somber remarks about the shooting from the White House on Monday, saying "our unity cannot be shattered by evil, our bonds cannot be broken by violence".

Republicans who control Congress have made clear they have no intention of taking up gun control measures, such as tightening restrictions on semiautomatic weapons and high-capacity magazines.

Trump, in a 2000 book, said that he supported a prohibition on assault weapons and a "slightly longer waiting period to purchase a gun". He also said in 2013 that he supported "background checks to weed out the sickos".

But Trump ran his campaign with a strong pro-Second Amendment message and the backing of the National Rifle Association.

"Gun and magazine bans are a total failure," read one campaign policy paper. "Opponents of gun rights try to come up with scary sounding phrases like 'assault weapons', 'military-style weapons' and 'high capacity magazines' to confuse people. What they're really talking about are popular semiautomatic rifles and standard magazines that are owned by tens of millions of Americans."

On Tuesday, Trump appeared somewhat open to having a debate on guns, but not anytime soon.

"At some point, perhaps, that will come," he told reporters. "But that's not for now."

AP