Treasury Secretary Steven Mnuchin said Thursday he will not attend an investment conference in Saudi Arabia.
The Saudis have said they plan to move forward with the conference, scheduled for October 23-25, despite a wave of cancellations by high-profile business, government and media leaders.
Trump said he hoped the Saudis' own investigation of Khashoggi's disappearance would be concluded in "less than a week".
The Foreign Minister of the Netherlands, Stef Blok, said he was pulling out because "the disappearance of Khashoggi is a very serious matter".
Pompeo is scheduled to brief Trump on the trip Thursday morning at the White House.
Saudi Arabia publicly pledged the payment to support US stabilization efforts in northeastern Syria in August, but questions persisted about when and if Saudi officials would come through with the money.
After Khashoggi was critical of President Donald Trump and the Saudi government's apparent trust in the United States leader, the royal family barred Khashoggi from writing.
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. Susan Collins tweeted. "We must get to the bottom of this, and if the Saudis killed Mr. Khashoggi, those responsible must be held accountable". Khashoggi had left the country a year ago amid the rise of Prince Mohammed, whom he wrote critically about in the Post.
According to Yeni Safak, Saudi Arabia's consul to Istanbul, Mohammed al-Otaibi, can be heard on one tape saying during Khashoggi's torture: "Do this outside".
Nationwide search continues for missing Wisconsin teen whose parents were killed
Jayme Closs is 5 feet tall, weighs 100 pounds and has green eyes and blond or strawberry hair, the sheriff's department said. When this investigation began, I knew I would need manpower to investigate and to search for Jayme and to bring her home.
"He was told, "Shut up if you want to live".
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 authorities say Khashoggi was killed.
The US secretary of state told reporters on Wednesday that he didn't want to get into specifics while discussing the circumstances surrounding the disappearance of Jamal Khashoggi, who was last seen entering the Saudi consulate in Istanbul, Turkey on October 2.
Plus, he said, Crown Prince MBS had made a "personal commitment" to Trump the night before last. "And that this report itself will be transparent, for everyone to see, to ask questions about", he continued.
On Tuesday, a high-level Turkish official told the AP that police found "certain evidence" of Khashoggi's slaying at the consulate, without elaborating. I didn't know what to do.
Khashoggi spoke of the peril that journalists who dare to criticize their governments face under an autocratic system, a reality that Khashoggi said was not likely to change and one that ultimately appears to have cost him his life.
"They have also arrested local reporters and pressured advertisers to harm the revenue of specific publications". The "final column" was published online Wednesday.
Saudi officials have strongly denied any involvement in his disappearance and say that he left the consulate soon after arriving.
This is a developing story, stay tuned for updates.