Turkish authorities say a team of Saudis killed Khashoggi, and United States intelligence intercepts show Saudi officials discussing an operation to lure Khashoggi - a Saudi citizen who had been living in the U.S. - back to Saudi Arabia from his home in Virginia and detain him.
"The kingdom's economy has an influential and vital role in the global economy, and that kingdom's economy is only affected by the global economy".
But both the White House and the kingdom are under mounting pressure as concern grows over the fate of the veteran journalist, who hasn't been seen since he entered the Saudi Consulate in Istanbul on October 2.
The warning from the world's top oil exporter came after a turbulent day on the Saudi stock exchange, which plunged as much as 7 per cent at one point.
Trump said that he had invited Khashoggi's fiancee, Hatice Cengiz, to visit him at the White House and that his staff was working out arrangements with her.
The journalist was once a Saudi government insider, but had gone into self-imposed exile in the US past year.
He had been living in a self-imposed exile in Washington D.C. for over a year when he went to the Saudi consulate on October 2 to obtain a document that would allow him to marry Cengiz.
Turkey said on Thursday it had accepted a proposal from Saudi Arabia to cooperate on the investigation.
The case risks damaging the image of the kingdom and its ties to the West as Crown Prince Mohammed bin Salman promotes a reform drive at home.
"Obviously I want to express concern for Mr. Khashoggi and his family", he added.
But Trump, who has frequently boasted about his business ties with the kingdom, suggested during the interview that ending US arms sales to Saudi Arabia would not be an option, saying, "I don't want to hurt jobs".
"It's clear, we can not have an ally who murders in cold blood, in their own consulate, a critic, a dissident, that is unacceptable", Sanders said.
Witt pointed out that Trump also has a personal interest in Saudi Arabia. His comments come after a bipartisan group of senators also proposed imposing sanctions on Riyadh over the matter.
'There needs to be a credible investigation to establish the truth about what happened, and - if relevant - to identify those bearing responsibility for the disappearance of Jamal Khashoggi, and ensure that they are held to account. However, the Khashoggi affair has caused technology executives and the media, including the Financial Times, Bloomberg, and CNN, to pull out of an investment summit in Riyadh scheduled for next week.
Khashoggi has written extensively for the Post about Saudi Arabia, criticizing its war in Yemen, its recent diplomatic spat with Canada and its arrest of women's rights activists after the lifting of a ban on women driving.
"Saudi Arabia, I get along with all of them", Trump said at the time. Those policies are all seen as initiatives of the crown prince.