U.S. President Donald Trump said Wednesday he addressed the disappearance of a Washington Post journalist with an unnamed senior Saudi leader at the "highest level."

"It's a very serious situation for us and this White House," Trump told reporters at the White House, noting talks have taken place "more than once."

"I think we'll get to the bottom of it," said Trump. "I'm not happy about this. We have to see what happens."

Jamal Khashoggi has been missing since visiting the Saudi Consulate in Istanbul Oct. 2.

His fiancee appealed to Trump to assist in efforts to find him Tuesday, penning an opinion piece in the Washington Post newspaper. 

"This much is true: He entered the consulate, and there’s no proof that he came out," wrote Hatice Cengiz.

"At this time, I implore President Trump and first lady Melania Trump to help shed light on Jamal’s disappearance. I also urge Saudi Arabia, especially King Salman and Crown Prince Mohammed bin Salman, to show the same level of sensitivity and release CCTV footage from the consulate," she added.

Trump said the White House has been in contact with Cengiz and hopes to meet her "fairly quickly."

He declined to comment on Khashoggi's possible fate, but said "we cannot let this happen; to reporters, to anybody."

The U.S. has been in contact with Turkish officials about the case, Trump said. 

Turkish security sources on Wednesday identified eight out 15 suspects linked to Khashoggi's disappearance.

According to the Turkish police sources, 15 Saudis, including several officials who arrived on the two planes, entered the consulate in Istanbul while Khashoggi was inside.

Prosecutors are investigating the incident, while the consulate said on Twitter it is working in coordination with Turkish authorities.

Turkey on Monday conveyed its expectation of "full cooperation" from Saudi Arabia in the search for the missing journalist.

Trump's National Security Advisor John Bolton and senior advisor Jared Kushner spoke with Saudi Crown Prince Mohammed Bin Salman about Khashoggi on Tuesday, the White House confirmed in a statement. 

Spokeswoman Sarah Sanders said Secretary of State Mike Pompeo also spoke to Salman in a "follow up call" that sought to "reiterate the United States request for information."

"In both calls they asked for more details and for the Saudi government to be transparent in the investigation process. We will continue to monitor this situation and provide updates as available,” she said.