U.S. President Donald Trump said Thursday he believes Jamal Khashoggi, a Saudi journalist and U.S. resident who went missing in Turkey earlier this month, is dead.

Asked if he thinks if Khashoggi is dead, Trump told reporters that it "certainly looks that way to me." Asked about the potential U.S. response should it be proven that Saudi authorities are responsible, he said, "It will have to be very severe."

It is the first time that Trump has acknowledged Khashoggi may be dead.

In an interview with the New York Times the same day, Trump said, "Unless the miracle of all miracles happens, I would acknowledge that he's dead."

Trump expressed confidence in intelligence reports from multiple sources that strongly suggest a high-level Saudi role in the apparent killing of Khashoggi, a critic of Saudi leaders.

A columnist for the Washington Post, Khashoggi vanished after entering the Saudi consulate in Istanbul on Oct. 2.

But Trump stopped short of saying Saudi's Crown Prince Mohammed bin Salman was responsible.

The president spoke after he was briefed on the case of Khashoggi by Secretary of State Mike Pompeo upon his return from a trip to Saudi Arabia and Turkey.

Earlier Thursday, Treasury Secretary Steven Mnuchin said he will not attend an investment forum slated for next week in Riyadh in response to the incident.

"I will not be participating in the Future Investment Initiative summit in Saudi Arabia," Mnuchin said in a Twitter post after meeting with Trump and Pompeo at the White House.

Aside from Mnuchin, other world leaders such as International Monetary Fund Managing Director Christine Lagarde, World Bank President Jim Yong Kim, and senior officials from Britain, France and the Netherlands have also decided to pull out of the Oct. 23-25 summit.

Known as "Davos in the Desert," the event, like annual meetings in the Swiss resort of Davos, brings together business and political leaders from around the world.