Washington(ANN)-Several US Republican senators have again rejected President Donald Trump’s defense of Saudi Arabia after the murder of Saudi journalist Jamal Khashoggi, with some lawmakers from his party saying Congress must take additional action.

Trump vowed last week to remain a “steadfast partner” of Saudi Arabia and said it was not clear whether Saudi Crown Prince Mohammed bin Salman knew about the plan to kill Khashoggi on October 2 at the Saudi consulate in Istanbul, Turkey.

The CIA believes bin Salman ordered the killing of Khashoggi, a US resident since 2017 and a columnist for the Washington Post who was critical of Saudi Arabia’s de facto leader.

However, the US president has cast doubt on the CIA assessment, telling reporters that the intelligence agency had not formed a definitive conclusion.

“I disagree with the president’s assessment. It’s inconsistent with the intelligence I’ve seen,” which implicates the crown prince, Republican Senator Mike Lee of Utah said Sunday on NBC’s “Meet the Press.”

He cited the Khashoggi killing as another reason why he has pushed against helping Saudi Arabia’s war effort in Yemen.

Earlier this month, the United States imposed economic sanctions on 17 Saudi officials for their role in the killing of Khashoggi and senators from both major US political parties introduced legislation that would suspend weapon sales to Saudi Arabia over Khashoggi and for its devastating military campaign in Yemen.

US Representative Adam Schiff, a Democratic from California, has promised investigations on the Khashoggi case as well as whether Trump’s personal financial interests are dictating his Saudi policy.

Schiff is in line to become chairman of the House of Representatives Intelligence Committee when Democrats regain control of the lower chamber of Congress in January.

“Look, the president is not being honest with the country about the murder of Jamal Khashoggi,” Schiff said on CNN’s “State of the Union” program. “What’s driving this?”

Riyadh initially denied knowledge of Khashoggi’s disappearance, then offered contradictory explanations.

Republican Senator Joni Ernst said it was very likely that bin Salman was involved in the murder, while acknowledging Saudi Arabia’s importance as a strategic partner for the US.

“And if there are indicators that the prince was involved in this murder then we need to absolutely consider further action.”

Republican Senator Ben Sasse, a frequent Trump critic, criticized Trump’s stance on Khashoggi’s killing as weak.

“Making the realist case is a different thing than being so weak that we failed to tell the truth, Sasse said on “Fox News Sunday.” Crown Prince Mohammed “contributed to murdering somebody abroad and it is not strength to sort of mumble past that. Strength is telling the truth even when it’s hard.”

Other Republican senators, including Lindsey Graham, Rand Paul and Bob Corker, have been unsparing in their assessments of Saudi Arabia’s involvement in Khashoggi’s killing.

“I never thought I’d see the day a White House would moonlight as a public relations firm for the Crown Prince of Saudi Arabia,” Corker, chairman of the Senate Foreign Relations Committee, wrote on Twitter after Trump’s comments on Tuesday.