*Trump briefed on killing by CIA, Pompeo

US President Donald Trump, while flying to California on Thursday, was briefed on the murder of Saudi journalist Jamal Khashoggi after a CIA assessment that Saudi Crown Prince Mohamed bin Salman ordered the killing, the White House said.

Trump discussed the CIA assessment by phone with the agency's director, Gina Haspel, and Secretary of State Mike Pompeo, White House spokeswoman Sarah Huckabee Sanders told reporters.

The CIA had briefed other parts of the US government, including Congress, on its assessment, sources told Reuters on Friday, a development that complicates Trump's efforts to preserve ties with the US ally.

The CIA's finding is the most definitive US assessment to date tying Saudi Arabia's de facto ruler directly to the killing and contradicts Saudi government assertions that Prince Mohamed was not involved.

However, the State Department said no "final conclusion" has been reached by the United States on who was behind the murder of Khashoggi.

"Recent reports indicating that the US government has made a final

conclusion are inaccurate. There remain numerous unanswered questions with respect to the murder of Khashoggi," spokeswoman Heather Nauert said in a statement.

"The State Department will continue to seek all relevant facts. In the meantime, we will continue to consult Congress, and work with other nations to hold accountable those involved in the killing of Jamal Khashoggi," she said.

Khashoggi, a US-based Washington Post columnist and critic of the crown prince, was killed in October at the Saudi consulate in Istanbul when he went there to pick up documents he needed for his planned marriage.

As lawmakers push legislation to punish Saudi Arabia for the killing, both Republican and Democratic senators on Saturday urged Trump to be tough on the crown prince, with whom he has cultivated a deep personal relationship.

"Everything points to the Crown Prince of Saudi Arabia, MbS, ordering @washingtonpost journalist Jamal #Khashoggi's killing. The Trump administration should make a credible determination of responsibility before MbS executes the men who apparently carried out his orders," tweeted Senator Bob Corker, chairman of the Senate Foreign Relations Committee, on Saturday.

Trump and top administration officials have said Saudi Arabia should be held to account for any involvement in Khashoggi's death and have imposed sanctions on 17 Saudis for their role in the killing.

But they have also stressed the importance of Washington's ties with Riyadh, one of the biggest clients of the US defense industry. Trump wants to preserve the Saudi arms deals, despite growing opposition in Congress.

"They have been a truly spectacular ally in terms of jobs and economic development," Trump said. "As president, I have to take a lot of things into consideration."

Marine General Joseph Dunford, chairman of the Joint Chiefs of Staff, noted on Saturday that the kingdom plays a key military role for the United States in the Middle East.

"Saudi Arabia has been an important partner to regional security in the past, I expect they will be in the future," he said at a security forum in Halifax, adding Middle Eastern allies including Saudi Arabia are "a stabilising force in the region".

On Thursday, Saudi Arabia’s public prosecutor said he was seeking the death penalty for five suspects charged in the killing of Khashoggi.

The prosecutor, Shaalan al-Shaalan, told reporters the crown prince knew nothing of the operation, in which Khashoggi’s body was dismembered and removed from the consulate.

Lawmakers critical of Saudi Arabia for Khashoggi's killing and its role in Yemen's civil war are ramping up their efforts to clamp down on the country.

"Trump must accept (for once) his intelligence experts’ incontrovertible conclusion: Crown Prince MbS is culpable for Khashoggi’s monstrous murder. This brazen killing must have consequences - sanctions, prosecution, removal of MbS & others, not continued cover-up, enabled by Trump," tweeted Democratic Senator Richard Blumenthal on Saturday.

US will hold killers to account: Pence

The US Vice-President Mike Pence has said that the United States would hold the murderers of Jamal Khashoggi to account.

"The United States is determined to hold all of those accountable who are responsible for that murder," Pence said on the sidelines of an APEC summit in Papua New Guinea.

He described the Saudi Journalist's murder as an "atrocity" and an "affront to a free and independent press" and added: "We are going to follow the facts." - QNA