Khashoggi, a Saudi national and U.S. resident who became increasingly critical of powerful Crown Prince Mohamed bin Salman, has not been seen since he walked into the Istanbul consulate to sort out marriage paperwork on October 2.
Saudi Arabia's government is discussing a plan to admit that missing journalist Jamal Khashoggi was killed after entering the Saudi consulate in Istanbul, three people with knowledge of the situation tell NBC News. "It sounded to me like maybe these could have been rogue killers".
Trump's comments came after a telephone conversation with King Salman, father of the crown prince, the first such talks since the crisis erupted.
Turkish officials believe Mr Khashoggi was murdered by Saudi agents but Riyadh has always strongly denied this.
Trump despatched Secretary of State Mike Pompeo for what the State Department described as "face to face meetings with the Saudi leadership" to find out what happened.
Saudi Arabia had on Saturday dismissed accusations that Khashoggi was ordered murdered by a hit squad inside its Istanbul consulate, labelling it as "lies and baseless allegations".
Saudi Arabia's sovereign wealth fund, the Public Investment Fund, which hosts the conference, invested $3.5 billion in Uber in 2016, making it one of the company's largest investors.
In other words: The Saudis' official defense is, reportedly, "We only wanted to torture and kidnap the dissident journalist, but the Crown Prince's friend got a little too enthusiastic, and accidentally killed him".
Australian share market tumbles 2 per cent on opening
Wednesday marked the largest single-day decline in the Dow Jones since February 8, when it fell 1,032 points to close at 23,860. All 30 of the Dow's stocks were in the red and it fell below 26,000 total points for the first time in a month, CNN reported .
Saudi officials previously have called the allegations "baseless", but reports in US media on Tuesday suggested the kingdom may acknowledge the writer was killed there.
The Journal, like CNN, said the Saudi statement has not been finalised.
Iran has lost some customers for its oil because of looming US sanctions, but high prices are making up for the lost sales, Iranian Vice President Eshaq Jahangiri has said.
A number of states, including Germany, France, Spain and the United Kingdom, have expressed serious concerns over the journalist's disappearance.
The Saudi riyal, rebounded early after falling to its lowest in two years over fears that foreign investment could shrink.
Khashoggi, a familiar face on Arab talk shows, moved to Washington previous year fearing retribution for his criticism of Prince Mohammed, who has cracked down on dissent with arrests. Saudi stock index was down 3 percent in early Tuesday trade before it recouped some losses for a decline of 0.5 percent by 0949 GMT.
"It should be a known fact that the Arabs never had a problem with antisemitism, but we need to state that over and over again", Khashoggi added, justifying the surprising Saudi presence at the event.
Other companies and high-profile businessmen have pulled out of the three-day conference known as "Davos in the desert", which is scheduled to begin on October 23 in Riyadh.
Prince Mohammed has aggressively pitched the kingdom as a destination for foreign investment.
Speaking of the Holocaust, Khashoggi called the chapter a disgusting episode in history, but also said that there were other awful events throughout history, such as the burning of Baghdad by the Mongols in the Middle Ages or the Palestinian Nakba.