Jamal Khashoggi at an event hosted by Middle East Monitor in London on September 29.
President Trump met with Secretary of State Mike Pompeo Thursday following Pompeo's fact-finding trip to Riyadh and Ankara.
The Dutch and French finance ministers, as well as several other politicians and business leaders, have said they are pulling out of the event.
"We made clear to them that we take this matter with respect to Mr. Khashoggi very seriously", Pompeo said following his almost hour-long briefing with the president.
The statement continued: "We encourage Turkish-Saudi collaboration and look forward to the Kingdom of Saudi Arabia conducting a thorough, credible, transparent, and prompt investigation, as announced". Trump and Pompeo are scheduled to meet at 10 a.m. ET on Thursday.
Senate Majority Leader Mitch McConnell, R-Ky., told reporters Wednesday the situation is "really going to challenge" the US relationship with Saudi Arabia, though said it's "too early to predict what the consequences will be".
Trump continued to stand by Saudi Arabia but said he is "not giving cover at all" to Riyadh, whom he repeatedly called a close USA ally.
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Saudi Arabia, which initially called the allegations "baseless", has not responded to repeated requests for comment from The Associated Press over recent days, including on Thursday.
Trump reiterated his hopes that Saudi leaders were not involved in the disappearance of Khashoggi, a U.S. resident. "This is the last piece of his I will edit for The Post", Attiah wrote.
Mashal Saad al-Bostani, a 31-year-old lieutenant of the Saudi Royal Air Force, was among the 15 suspects who arrived and left Turkey on October 2 after going to Saudi Arabia's Istanbul consulate where Khashoggi was last seen, Hurriyet Daily News quoted the Turkish newspaper Yeni Safak as saying in the report.
Citing the $110 billion U.S. -Saudi arms deal, of which only $14.5 billion is finalized, he said, "It'll be a lot of money coming to our coffers, and it's not something that you want to blow up willy-nilly".
In this December 15, 2014 file photo, Jamal Khashoggi, then general manager of a new Arabic news channel speaks during a press conference, in Manama, Bahrain.
Turkish officials believe Mr Khashoggi was killed by a team of Saudi agents inside the consulate, with his body then removed.
At the White House Wednesday, President Trump said he's still waiting to find out what happened before jumping to conclusions. "If it exists we have asked for it", Trump told reporters in the Oval Office.
"It is 500,000 jobs, it will be ultimately $110 billion, it's the biggest order in the history of our country from an outside military, and I said we are gonna turn that down?" he added. I didn't know what to do. His killers later beheaded and dismembered him, it said. "They not only kill him in the consulate, but also in a barbaric way". Khashoggi first began writing for the Post's opinion section in September 2017, and his columns criticized the prince and the direction of the Saudi kingdom.