United States (US) President Donald Trump described the killing of Saudi journalist Jamal Khashoggi as a botched operation and a “bad original concept” as his administration took its first, careful steps toward punishing the Saudis by moving to revoke the visas of the suspects.

Speaking to reporters at the White House, Trump said the entire operation was a fiasco.

“They had a very bad original concept,” Trump said on Tuesday. “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.”

Even in the face of ugly details of Jamal Khashoggi's slaying, Trump has resisted calls to cut off arms sales to the kingdom and has been reluctant to antagonise the Saudi rulers. Trump considers the Saudis to be vital allies in his Mideast agenda.

Members of Congress have demanded that sanctions be imposed on Saudi Arabia over the killing of Khashoggi, who lived in self-imposed exile in the US and wrote critically about Saudi Crown Prince Mohammed bin Salman.

The writer, who was a contributor to The Washington Post, vanished on Oct 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. Saudi officials after weeks of denials now concede that he died, but they say it happened accidentally in a fight at the consulate.

“It was a total fiasco,” Trump said. “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.”

Secretary of State Mike Pompeo said the move to revoke visas was just a first step.

Visa records are confidential and Pompeo was not more 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,” Pompeo told reporters at the State Department.

The administration “will continue to hold those responsible accountable. 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.”

Still, Pompeo stressed the strategic importance of the US-Saudi relationship.

“We continue to view as achievable the twin imperative of protecting America and holding accountable those responsible for the killing of Mr Khashoggi,” Pompeo said.