US President Donald Trump has defended Saudi Arabia’s crown prince Mohammed bin Salman in the killing of journalist Jamal Khashoggi, saying “things happen” and the royal “knew nothing” of the assassination by Saudi agents.

The statements, as Trump lavished praise on bin Salman on Tuesday on his first visit to the White House in more than seven years, contradicts the conclusions of US intelligence agencies.

They found that Khashoggi, a Washington Post columnist who had been critical of bin Salman and his policies, was murdered by a team of Saudi agents in the kingdom’s consulate in Istanbul in October 2018. His dismembered body has never been recovered.

The crown prince has denied ordering the operation but acknowledged responsibility as the kingdom’s de facto ruler.

“A lot of people didn’t like that gentleman that you’re talking about, whether you like him or didn’t like him,” Trump said next to bin Salman in the Oval Office.

“Things happened, but he knew nothing about it, and we can leave it at that.”

Bin Salman said it had been “painful” to hear about Khashoggi’s death but that his government “did all the right steps of investigation”.

“We’ve improved our system to be sure that nothing happened like that. And it’s painful and it’s a huge mistake,” he said.

Trump, who chided the reporter who asked the Khashoggi question “to embarrass our guest”, also praised the crown prince for doing an “incredible” job on human rights but did not elaborate.

Trump’s treatment of bin Salman prompted a rebuke from Khashoggi’s widow.

“There is no justification to murder my husband. While Jamal was a good transparent and brave man, many people may not have agreed with his opinions and desire for freedom of the press,” Hanan Elatr Khashoggi wrote on X, urging bin Salman to meet her.

Bin Salman has been strongly criticised by human rights groups not only for the Khashoggi killing but for his crackdown on dissent at home. But the crown prince has also unleashed major social reforms that have swept away some austere social codes.

At the start of his visit, with which bin Salman sought to further rehabilitate his global image tarnished by the Kashoggi killing, the crown prince was greeted with a lavish display of pomp and ceremony presided over by Trump on the South Lawn. It came with a military honour guard, a cannon salute and a flyover by US warplanes.

The meeting underscored a key relationship – between the world’s biggest economy and the top oil exporter – that Trump has made a high priority in his second term as the international uproar around the killing of Khashoggi, a Saudi insider-turned-critic, has gradually faded.

The warm welcome for bin Salman in Washington marks a high point for the US-Saudi ties, which had suffered because of Khashoggi’s murder.

Sitting next to Trump, bin Salman promised to increase his country’s US investment to $US1 trillion ($A1.5 trillion) from a $US600 billion ($A922 billion) pledge he made when Trump visited Saudi Arabia in May. But he offered no details or timetable.

A $US1 trillion investment in the US would be difficult for Saudi Arabia to pull together given its heavy spending on an already-ambitious series of massive projects at home, including futuristic megacities that have gone over budget and faced delays and stadiums for the 2034 World Cup.

‘Quiet piggy’

The White House meeting came just hours after astonishing footage emerged of Trump calling a journalist “piggy” as she questioned him about the Jeffrey Epstein case.

CNN video of the incident aboard Air Force One on Friday (US time) emerged on Tuesday.

Asked about recently released Epstein emails that mentioned him, Trump again denied any knowledge and said the focus should be on others who were named, including former US president Bill Clinton.

When a Bloomberg News journalist Catherine Lucey tried to ask a follow-up question on Epstein, Trump turned to her and said: “Quiet. Quiet, piggy.”

The exchange occurred amid growing calls for the US Department of Justice to release files related to its investigation into Epstein, the late financier and convicted sex offender who died in prison in 2019.

Also on Tuesday, the US House of Representatives overwhelmingly passed a bipartisan bill to compel the release the department’s case files. It followed Trump dropping his long-standing opposition on Sunday, days after a House petition gathered enough support to force a vote.

-with AAP