As President Donald Trump is denouncing the “deception” and “lies” coming from the Saudi government, members of Congress from his own party are pushing the president toward a more forceful response that squarely blames the Saudi crown prince for the death of dissident journalist Jamal Khashoggi.

While Trump is hesitant to directly fault Mohammed bin Salman for Khashoggi’s killing, and praised him on Saturday as a “strong person,” lawmakers who have been briefed on the matter say they are all but certain the crown prince is responsible for the Washington Post columnist’s death. A few have expressed discomofort about moving forward with arms sales to the kingdom.

“It is my thinking that MBS was involved in this, that he directed this, and that this person was purposely murdered,” Sen. Bob Corker (R-TN), the chairman of the Senate Foreign Relations Committee, said Sunday on CNN’s State of the Union. “My guess is at the end of the day, the United States and the rest of the world will believe fully that he did it. We’ll see.”

The Saudi government admitted over the weekend that Khashoggi is dead, and claimed that he died after a “fist fight” led to his strangulation inside the Saudi consulate in Istanbul. Corker said he does not find that explanation credible, breaking with Trump who said on Friday that he believed the newest Saudi line. Saudi officials initially claimed that Khashoggi—a Saudi citizen who was a legal U.S. resident—walked out of the consulate, unharmed, through a back entrance.

This weekend, the Saudi government said it arrested 18 Saudi nationals in connection with the killing and that the crown prince sacked a handful of top officials. But the government has yet to account for its shifting narratives, and it has not answered questions about what happened to Khashoggi’s body.

“They’ve lost all credibility as it relates to explaining what has happened,” Corker said.

Corker added that he expects the U.S. to soon receive audio from the Turks that purports to be from Khashoggi’s killing inside the consulate, where Khashoggi was visiting earlier this month in order to receive official documents. Based on that audio, the Turks had privately concluded—but have yet to publicly acknowledge—that Khashoggi was murdered and that his body was dismembered.

The senator added that “there has to be a punishment and a price paid” if an independent investigation finds that the crown prince ordered Khashoggi’s murder. Senate Minority Whip Dick Durbin (D-IL) went as far as to suggest a punishment in the meantime: expelling the Saudi ambassador to the U.S.

“Unless the Saudi kingdom understands that civilized countries around the world are going to reject this conduct and make sure that they pay a price for it, they’ll continue doing it,” Durbin said on NBC’s Meet the Press.

The Trump administration has invested significant political capital in its relationship with Saudi Arabia, viewing the country as key to its Middle East peace plan. Trump told The Washington Post that he “would love if [the crown prince] wasn’t responsible.”

Even so, the administration is considering a number of options as punishment for Khashoggi’s death, including human-rights sanctions targeting, among other top officials, the crown prince himself. But there is a growing rift between Capitol Hill and the White House over Trump’s reluctance to end U.S. weapon sales to Saudi Arabia. Trump has said he is willing to work with Congress on ways to punish the Saudi government, but he maintained that the arms sales are important for the U.S. economy. Some of the president’s allies are urging him to cut the Saudis off as they use U.S. weapons to exacerbate a bloody civil war in Yemen.

“There’s no way 15 people were sent from Saudi Arabia to Turkey to kill a dissident without the approval of the crown prince. And that’s why I say we have to be stronger than just saying, ‘oh, we’re going to sanction a few of these people and pretend like we’re doing something,’” Sen. Rand Paul (R-KY), who has tried in the past to block arms sales to Saudi Arabia, said on Fox News Sunday.

“I think we really need to discontinue our arms sales to Saudi Arabia and have a long and serious discussion about whether or not they want to be an ally or they want to be an enemy,” Paul added, calling Saudi Arabia’s latest explanation for Khashoggi’s death “insulting to anyone who is analyzing this with any kind of intelligent background.”