(CNN) President Donald Trump offered his most stinging indictment yet of a Saudi effort to silence a dissident journalist, calling the series of events that led to Jamal Khashoggi's death "the worst cover up ever."

"The cover up was one of the worst in the history of cover ups," Trump said from the Oval Office. "It's very simple."

Later Tuesday, Trump went further, calling the episode a "total fiasco."

The rebuke of Saudi Arabia's response to the death reflected Trump's growing frustration at the diplomatic crisis, which has thrust his foreign policy objectives into a harsh spotlight. It came amid an evolving administration response, which including dispatching the CIA director to Turkey to gather more details.

The President has become increasingly irritated by the fallout from Khashoggi's death, multiple sources who have heard him voice his frustration told CNN.

Visas to be revoked

On Tuesday, Secretary of State Mike Pompeo said the US will be revoking the visas of those who murdered the Washington Post journalist, and said that the administration has "identified at least some of the individuals responsible."

The top US diplomat said that the State Department is also working with the Treasury Department to apply human rights-related sanctions that includes the freezing of assets and a travel ban.

After Pompeo spoke, State Department spokesperson Heather Nauert announced that "21 Saudi suspects in the death of Jamal Khashoggi will have their visas revoked or be ineligible for a visa to enter the United States." Another State Department spokesperson told CNN that State wouldn't be identifying the individuals because "visa confidentiality, protected by U.S. law, prohibits us from discussing individual visa cases."

Saudi Arabian officials have said the October 2 killing, inside the Saudi consulate in Istanbul, was part of a rogue operation gone wrong. Foreign Minister Adel al-Jubeir told Fox News on Sunday that Khashoggi's death was a "tremendous mistake" and added that his government would punish those responsible for his "murder."

Trump, however, seemed less willing to accept that official explanation. He cast the situation as a lousy attempt at concealing a crime.

"Somebody really messed up," he said. "Because whoever thought of that idea, I think is in big trouble. And they should be in big trouble."

He said he was expecting to hear more from US intelligence officials during a meeting on Wednesday afternoon.

"However they talk about it, nothing they've done has gone well. It certainly has not been spoken of properly," he said, flanked by US military brass. "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."

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Khashoggi son meets King, Crown Prince

Salah Khashoggi, the son of the slain journalist, and another relative, Sahl bin Ahmad Khashoggi, were summoned to the Al Yamama Palace in Riyadh, the Saudi Press Agency (SPA) reported Tuesday, where they met the King and the Crown Prince.

The King and Crown Prince "expressed their sincere condolences to the family of Jamal Khashoggi -- may God have mercy on him," SPA reported.

Salah, who lives in the Saudi city of Jeddah, has been unable to travel outside Saudi Arabia for several months, as his passport had been invalidated, according to sources close to the family.

Other members of Khashoggi's family, including his ex-wife and daughter, are currently in Dubai, add the sources.

Saudi Crown Prince Mohammed bin Salman and his father King Salman pictured shaking hands with Salah Khashoggi, the journalist's eldest son, and Sahl bin Ahmad Khashoggi, another relative, at Al Yamama Palace in Riyadh.

Trump: Erdogan 'rough' on Saudi Arabia

He described an earlier phone call with Turkish President Recep Tayyip Erdoğan as damning for Saudi Arabia.

"He was pretty rough on Saudi Arabia, I would say," Trump said.

In recent days, the President has complained about the negative coverage blanketing cable television and told confidantes he feels betrayed by the Saudis, who have presented shifting accounts about what happened to the journalist after he entered the Saudi consulate in Turkey three weeks ago to obtain a marriage document and never left.

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The President, who spoke Sunday with Saudi Arabia's Crown Prince Mohammed bin Salman, is privately blaming them for making him look bad. At times he has talked about how much he has done so much for the Saudis, complaining that they put him in this position.

Trump doesn't like that he and his son-in-law and senior adviser Jared Kushner have been depicted as overly cozy with the Saudis.

Saudi officials claim Khashoggi died in a fistfight involving more than a dozen Saudi officials at the country's consulate in Istanbul. Advisers have told Trump that that explanation for Khashoggi's death does not add up.

While departing the White House for a rally Monday in Texas, Trump appeared skeptical of the Saudi explanation and suggested he wouldn't accept the one month the Saudis have requested to complete their investigation into Khashoggi's death.

"I am not satisfied with what I've heard," Trump said. "That's a long time. There's no reason for that much. Be faster."

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Aides: Murder not an election issue

But White House aides have told the President that Khashoggi's death isn't an issue that resonates with their base and are confident it won't affect Republicans' chances in the upcoming midterm elections.

Trump is being advised to focus his messaging on the caravan, which officials think is a winning issue for Republicans two weeks before voters go to the polls. Trump hasn't mentioned the Saudi situation at any of his campaign rallies in the past several weeks.

As Trump assailed the shifting Saudi story about Khashoggi's fate, Saudi officials offered more details of the events surrounding the Virginia resident's death, but provided no corroborating evidence.

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Elaborate plan described

They described a plan to convince Khashoggi to return to Saudi Arabia. If he refused, an official told CNN, the next step was to drug the journalist with a tranquilizer and take him to a safe house in Istanbul for 48 hours. If Khashoggi still refused to return to Saudi Arabia at that point, the team was to leave and a "local collaborator" was to let him go, the source claimed.

The Saudi official also claimed that the forensic expert who was part of the team was there to wipe all evidence of Khashoggi's presence at the consulate and the safe house, so that if Khashoggi claimed later that he had been kidnapped, there would be no proof. The New York Times has reported that the forensic expert was equipped with a bone saw.

The official said that of the 15 Saudis who took part in the operation, a total of nine were at the consulate, with "three or four to question him and the rest to handle logistics." There was no explanation why three to four people would be needed for questioning, or what logistics the others would attend to.

The rest of the Saudi squad, including generals and their security detail, waited at the safe house, according to the source.

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Beaten, tortured, dismembered

Turkish officials have said that Khashoggi was set upon immediately after entering the consulate, and then beaten, tortured and dismembered.

The Saudi official told CNN that Khashoggi became agitated after being told he would be drugged and taken to a safe house, at which point he tried to resist, was put in a chokehold and killed.

CIA Director Gina Haspel is on the ground in Turkey Tuesday reviewing evidence in Khashoggi's murder investigation. Vice President Mike Pence, who pledged Tuesday during an interview with The Washington Post that his death "will not go without an American response," said she will brief him and Trump upon her return.

Both Trump and Pompeo said on Tuesday the US would continue to probe for answers.

"This is certainly not the last step, we will continue to do our own efforts, our own fact finding," Pompeo said, while adding that the US will also take into account information from Turkey and Saudi Arabia.

"We want to make sure everyone understands that the United States believes that the killing of Jamal Khashoggi wasn't anything other than a horrific act," Pompeo said.