Leading US senators say they are more certain than ever Saudi Crown Prince Mohammed bin Salman is responsible for the killing of journalist Jamal Khashoggi after they received a CIA briefing on the matter.

Key points: Both Republicans and Democrats said they still want to pass legislation to send a message to Saudi Arabia

Both Republicans and Democrats said they still want to pass legislation to send a message to Saudi Arabia CIA Agency Director Gina Haspel briefed the senators on the information available on the Khashoggi murder

CIA Agency Director Gina Haspel briefed the senators on the information available on the Khashoggi murder President Trump has argued that Washington should not take action that would risk its relationship with Riyadh

"You have to be wilfully blind not to come to the conclusion that this was orchestrated and organised by people under the command of MbS," Republican senator Lindsey Graham told reporters, referring to the Crown Prince by his initials.

In his bid to pressure the Trump administration to condemn the Crown Prince, Senator Graham said there may not be a "smoking gun," but that there was a "smoking saw", a reference to a bone saw that investigators said was used to cut up Khashoggi's body.

Senator Graham said the Saudi royal was "a wrecking ball", "crazy" and "dangerous".

Making some of their strongest accusations so far, both Republicans and Democrats said they still wanted to pass legislation to send a message to Saudi Arabia that the United States condemned the death of Khashoggi.

Saudi Crown Prince Mohammed bin Salman watches on as world leaders arrive at the G20 Summit. (Reuters: Kevin Lamarque)

And they urged US President Donald Trump himself to strongly condemn the killing after he stood by the Crown Prince.

"If the Crown Prince went in front of a jury, he'd be convicted in 30 minutes," said Senator Bob Corker, the Republican chairman of the Senate Foreign Relations Committee.

Asked if he would be convicted of murder, Senator Corker replied: "Yes."

The senators spoke to reporters as they left a closed-door briefing for some Senate committee leaders and Senate leaders by CIA director Gina Haspel.

"The views that I had before have only solidified," said senator Bob Menendez, the top Democrat on the Foreign Relations Committee.

Last week, 14 of Mr Trump's fellow Republicans, who hold a slim majority in the Senate and rarely break from the President, defied his wishes and voted with Democrats to advance a measure that would end US support for the Saudi-led war effort in Yemen.

Donald Trump is standing by Saudi Arabia and Crown Prince Mohammed bin Salman. (Reuters: Jonathan Ernst)

The unusual vote came shortly after a briefing by Mr Trump's Secretary of State, Mike Pompeo, and Secretary of Defence Jim Mattis, who urged senators not to do anything to undermine the US-Saudi relationship.

Ms Haspel's absence from that briefing angered senators.

Senator Corker shook his head, when asked if he thought Ms Haspel's briefing had changed any minds.

Khashoggi, a US resident who wrote for the Washington Post, was killed inside the Saudi consulate in Istanbul in October.

Senators made clear there were still deep divides between the two parties on how to proceed.

Jamal Khashoggi was killed in the Saudi consulate in Istanbul. (AP: Hasan Jamali, file photo)

Senator Corker said it would be "difficult" to come up with legislation that could pass the Senate.

He said he was working with colleagues on how to amend the resolution, and he had not had suggestions from the Trump administration on how it might prefer to proceed.

Many Democrats want a "straight up or down vote" on the resolution to end all US support for the Saudi coalition in Yemen, without amendments.

But Mr Trump, and some of his fellow Republicans, have argued Washington should not take action that would risk its relationship with Riyadh, which is viewed as an important counterweight to Iran in the Middle East.

Republican senator Richard Shelby underscored that point in his comments after the meeting with Ms Haspel.

"Somebody should be punished," he said. "Now the question is how do you separate the Saudi Crown Prince and his group from the nation itself?"

Reuters