According to the CIA findings, 15 Saudi agents flew on government aircraft to Istanbul and assassinated Khashoggi in the Saudi consulate, the Post said.
Queried by AFP, the CIA declined to comment.
Khashoggi, a Washington Post columnist, had gone to the consulate to obtain documents necessary to marry his Turkish fiancee.
Saudi Arabia has repeatedly changed its official narrative of the October 2 murder, first denying any knowledge of Khashoggi’s whereabouts and later saying he was killed when an argument degenerated into a fistfight.
In the latest version presented by the Saudi prosecutor on Thursday, a 15-member squad was formed to bring Khashoggi back from Istanbul “by means of persuasion” — but instead ended up killing the journalist and dismembering his body in a “rogue” operation.
The CIA scrubbed multiple intelligence sources, the Post said, among them a phone call between the prince’s brother — the Saudi ambassador to the United States — and Khashoggi.
The ambassador reportedly told the late journalist that he would be safe to go to the consulate in Istanbul and get the papers he needed.
The US intelligence agency also said in determining the Crown Prince’s role it considered him a “de facto ruler” in Saudi Arabia: “The accepted position is that there is no way this happened without him being aware or involved,” the Post quoted an official as saying.
That official dubbed Prince Mohammed a “good technocrat” — but also someone unpredictable who “goes from zero to 60, doesn’t seem to understand that there are some things you can’t do.”
The CIA conclusions threaten to further fray relations between Washington and key ally Riyadh, which has sought to end discussion of Khashoggi’s murder and rejected calls for an international investigation.
On Thursday the US Treasury slapped sanctions on 17 people, including close aides of Prince Mohammed, suggesting a coordinated effort between Riyadh and Washington to pre-empt the threat of harsher actions from an outraged US Congress.