Several U.S. Republican senators on Sunday rejected President Donald Trump’s embrace 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 last month at the Saudi Consulate in Istanbul.

The president cast doubt on the CIA assessment that Crown Prince Mohammed ordered Khashoggi’s killing, telling reporters that the 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 Sen. Mike Lee said 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.

The United States on Nov. 15 imposed economic sanctions on 17 Saudi officials for their role in the killing of Khashoggi and senators from both major U.S. parties introduced legislation that would suspend weapon sales to Saudi Arabia over Khashoggi and for its role in Yemen’s civil war.

Democratic U.S. Rep. Adam Schiff, who is in line to become chairman of the House Intelligence Committee when Democrats regain control of the chamber in January, has promised investigations on the Khashoggi case as well as whether Trump’s personal financial interests are dictating his Saudi policy.

“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?”

Khashoggi, a Washington Post columnist and critic of the crown prince, was killed Oct. 2. Riyadh initially denied knowledge of Khashoggi’s disappearance, then offered contradictory explanations.

“I do think we need to look into this further,” Republican Sen. Joni Ernst said on CNN.

Ernst acknowledged Saudi Arabia’s importance as a strategic partner.

“However, we also are a very strong nation when it comes to human rights, when it comes to the rule of law,” Ernst said.

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

Sen. 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.