Donald Trump has said the killing of journalist Jamal Khashoggi was "one of the worst cover-ups in the history of cover-ups".
Addressing reporters at the White House, the US president said the entire operation was "a very bad original concept", adding that "somebody really messed up".
'A very bad original concept'
"They had a very bad original concept," Mr Trump said. "It was carried out poorly, and the cover-up was one of the worst cover-ups in the history of cover-ups. Somebody really messed up, and they had the worst cover-up ever."
He added: "The process was no good. The execution was no good. And the cover-up, if you want to call it that, was certainly no good."
The US is now taking steps to revoke the visas of the suspects in the murder.
Secretary of State Mike Pompeo said a move to revoke visas was just a first step.
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Visa records are confidential and Mr Pompeo was not specific about who the revocations would affect, but the State Department later said 21 "Saudi suspects" would have visas revoked or would be declared ineligible to enter the US.
"These penalties will not be the last word on this matter," Mr Pompeo told reporters.
"We're making very clear that the United States does not tolerate this kind of ruthless action to silence Mr Khashoggi, a journalist, with violence," he said. "Neither the president or I am happy with this situation."
However, Mr Trump has resisted calls to cut off arms sales to Saudi Arabia, with the country considered one of America's vital allies.
Mr Khasoggi, who was a contributor to The Washington Post, vanished on October 2 after entering the Saudi consulate in Turkey, where he went to pick up documents for his marriage to his Turkish fiancee.
Turkish officials say that a Saudi team of 15 men tortured, killed and dismembered the writer and that Saudi officials had planned the killing for days.