Defense Secretary James Mattis stressed on Wednesday that the U.S. government does not have a "smoking gun" that implicates Saudi Crown Prince Mohammed bin Salman, known as MBS, in the brutal murder of dissident writer Jamal Khashoggi.

"We have no smoking gun that the crown prince was involved, not the intelligence community or anyone else," Mattis told reporters before an event at the Pentagon with his Lithuanian counterpart. "There is no smoking gun."

He added that he does not believe the U.S. government possess audio tapes from the day Khashoggi was killed and reportedly dismembered inside the Saudi consulate in Istanbul, Turkey. "We do not have the tapes. At least I'm not aware that we do," he said.

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Mattis noted, however, that he has read the translations of the tapes during intelligence briefings. The former Marine Corps general said the American government is committed to holding those responsible for the high-profile assassination accountable.

CBS News has reported that the CIA has intelligence substantiating an assessment that Saudi Crown Prince Mohammed bin Salman ordered the killing of journalist Jamal Khashoggi.

On Tuesday, National Security Adviser John Bolton said he saw no point in listening to the tape of Khashoggi's murder because he does not understand Arabic. "I'm very satisfied that we know what the tape picked up, and it was factored into the president's decision, and he's announced his position very clearly," Bolton said.

CIA Director Gina Haspel, reportedly the highest ranking official in the Trump administration who has listened to the tape, did not join Mattis and Secretary of State Mike Pompeo in a Capitol Hill meeting on military assistance to the Saudi kingdom on Wednesday.

Senators suggested that the White House is barring Haspel from briefing lawmakers on the audio recording provided by the Turks, but CIA Press Secretary Timothy Barrett said the "notion that anyone told Director Haspel not to attend today's briefing is false."

Mattis said senators expressed frustration during the meeting, not only about Khashoggi's assassination, but about the dire humanitarian crisis in Yemen, where a Saudi-led coalition with American assistance is waging a bloody war against the Iranian-backed Houthi rebels.

The defense secretary also told reporters that the troop deployment in the southern border might extend beyond the Dec. 15 deadline if the Department of Homeland Security requests more logistical assistance.

And he weighed in on the seizure of three Ukrainian naval ships by the Russian navy on Sunday, calling the incident a "flagrant violation of international law."