US president Donald Trump acknowledged that it “certainly looks” as though missing Saudi journalist Jamal Khashoggi is dead, and he threatened “very severe” consequences if the Saudis are found to have murdered him.

His warning came as the administration toughened its response to a disappearance that has sparked global outrage.

Before Mr Trump spoke, the administration announced that Treasury Secretary Steven Mnuchin had pulled out of a major upcoming Saudi investment conference and a US official said Secretary of State Mike Pompeo had warned the Saudi crown prince that his credibility as a future leader was at stake.

Mr Pompeo said the Saudis should be given a few more days to finish and make public a credible investigation before the US decides “how or if” to respond.

Mr Trump’s comments, however, signalled an urgency in completing the probe into the disappearance of the journalist, last seen entering the Saudi Consulate in Istanbul on October 2.

Turkish reports say Mr Khashoggi, who had written columns critical of the Saudi government for The Washington Post over the past year while he lived in self-imposed exile in the US, was killed and dismembered inside the Saudi Consulate in Istanbul by members of an assassination squad with ties to Saudi Crown Prince Mohammed bin Salman.

The Saudis have dismissed those reports as baseless but have yet to explain what happened to the writer.

Leading human rights and journalists’ organisations have urged Turkey to ask the United Nations to launch an investigation into the disappearance and “possible extrajudicial execution” of Mr Khashoggi.

Mr Trump, who has insisted that more facts must be known before making assumptions, did not say on what he based his latest statement about the writer’s likely demise.

Asked if Mr Khashoggi was dead, he said, “It certainly looks that way. … Very sad.”

A security guard stands behind barriers blocking the road leading to the Saudi Arabia consulate in Istanbul
A security guard stands behind barriers blocking the road leading to the Saudi Arabia consulate in Istanbul (AP Photo/Lefteris Pitarakis)

Asked what consequence Saudi leaders would face if they are found to be responsible, he replied: “It will have to be very severe. It’s bad, bad stuff. But we’ll see what happens.”

Vice-president Mike Pence said earlier in Colorado that “the world deserves answers” about what happened to Mr Khashoggi, “and those who are responsible need to be held to account”.

In Istanbul, a leaked surveillance photo showed a man who has been a member of the crown prince’s entourage during trips abroad walking into the Saudi Consulate just before Mr Khashoggi vanished there — timing that drew the kingdom’s heir-apparent closer to the columnist’s apparent demise.

Turkish officials say Maher Abdulaziz Mutreb flew into Istanbul on a private jet along with an “autopsy expert” on October 2 and left that night.

In Washington, Mr Pompeo, who was just back from talks with Saudi and Turkish leaders, said of the investigations in Istanbul: “I told President Trump this morning that we ought to give them a few more days to complete that so that we, too, have a complete understanding of the facts surrounding that, at which point we can make decisions about how, or if, the United States should respond to the incident surrounding Mr Khashoggi.”

UN spokesman Stephane Dujarric said secretary-general Antonio Guterres remained very concerned about Mr Khashoggi’s fate and “has repeatedly called for the truth to come out in this situation”.

“As a matter of principle, the secretary-general can initiate an investigation if all the parties involved request it, or if there’s a legislative mandate from a UN body,” Dujarric said. “We’re a little removed right now. … I think we need to let the initial investigation play out.”