One source says the report will likely conclude that the operation was carried out without clearance and transparency and that those involved will be held responsible.
One of the sources acknowledged that the report is still being prepared and cautioned that things could change.
The Washington Post columnist was last seen in public when he entered the Saudi consulate in Istanbul in Turkey on October 2.
Previously, Saudi authorities had maintained Khashoggi left the consulate the same afternoon of his visit, but provided no evidence to support the claim.
Khashoggi's fiancée, Hatice Cengiz, who was waiting outside the consulate, says she did not see him re-emerge.
The disappearance created a diplomatic rift between Saudi Arabia and the West. Amid the fallout, international firms pulled out of a high-profile investment summit, the Future Investment Initiative conference, due to take place later this month in Riyadh.
The case also caused friction between Saudi Arabia and Turkey, which has repeatedly accused the Saudis of failing to cooperate with their investigation.
Turkish authorities previously said they believed that 15 Saudi men who arrived in Istanbul on October 2 were connected to Khashoggi's disappearance and possible murder. At least some of them appear to have high-level connections in the Saudi government.
On Friday, a source familiar with the investigation told CNN that Turkish authorities have audio and visual evidence that shows journalist Khashoggi was killed inside the consulate.
CNN reporters saw Turkish investigators, including forensics officers, entering the Saudi consulate in Istanbul Monday evening. Saudi officials had granted permission for the premises to be searched, a Turkish diplomatic source told CNN, and police were seen cordoning off the area before investigators arrived. Turkish officials also wanted to search the nearby consul general's residence.
Trump also said he dispatched Secretary of State Mike Pompeo to meet with King Salman, during a Sunday night phone call.
On the airplane, State Department Spokesperson Heather Nauert told reporters that Secretary Pompeo "looks forward to meeting with King Salman."