Sen. Lindsey Graham (R-S.C.), one of President Trump’s staunchest allies, warned the president on Tuesday that ignoring Saudi Arabia’s bad behavior would risk America’s moral leadership on the world stage.

Graham, chairman of the Appropriations Subcommittee on State, Foreign Operations and Related Programs, said Saudi Arabia must be held accountable for the death of U.S.-based journalist Jamal Khashoggi, who was killed after entering the Saudi consulate in Istanbul on Oct. 2.

“It is not in our national security interests to look the other way when it comes to the brutal murder of Mr. Jamal Khashoggi,” Graham said in a statement released late Tuesday afternoon.

{mosads}The South Carolina Republican, who is set to become chairman of the Senate Judiciary Committee in January, warned that Trump’s tolerant stance toward Saudi Arabia threatened to risk the nation’s role as a moral leader.

“I fully realize we have to deal with bad actors and imperfect situations on the international stage,” Graham said. “However, when we lose our moral voice, we lose our strongest asset.”

Trump in a statement released earlier Tuesday defended Saudi Arabia as an important counterweight in the Middle East to Iran and extolled what he described as a Saudi pledge to spend $450 billion in the United States.

The president also questioned whether Saudi Crown Prince Mohammed bin Salman was involved in Khashoggi’s death, despite the CIA reportedly concluding that the crown prince was responsible for the journalist’s murder.

Trump on Tuesday noted that King Salman and the crown prince have vigorously denied any knowledge of the planning or execution of Khashoggi’s murder. 

“Our intelligence agencies continue to assess all information, but it could very well be that the Crown Prince had knowledge of this tragic event – maybe he did and maybe he didn’t!” Trump said in his statement.

He later told reporters at the White House that breaking with Saudi Arabia, an influential member of the OPEC would send oil prices “through the roof.”

Graham on Tuesday afternoon said the Senate should take action by voting on sanctions legislation.

“I firmly believe there will be strong bipartisan support for serious sanctions against Saudi Arabia, including appropriate members of the royal family, for this barbaric act which defied all civilized norms,” he said in his statement. “While Saudi Arabia is a strategic ally, the behavior of the Crown Prince – in multiple ways – has shown disrespect for the relationship and made him, in my view, beyond toxic.”

The administration imposed sanctions on 17 Saudis believed to be involved in the murder of Khashoggi, who wrote for The Washington Post.

Graham is one of several Republican co-sponsors of the Saudi Arabia Accountability and Yemen Act, which would suspend weapons sales to Saudi Arabia, prohibit U.S. planes from refueling Saudi-led coalition aircraft involved in the civil war in neighboring Yemen, and require a report on human rights abuses in Saudi Arabia.

Graham became the second Senate Republican to break with Trump over his statement Tuesday questioning whether the crown prince was involved in Khashoggi’s death and proclaiming Saudi Arabia a “steadfast partner.”

Sen. Rand Paul (R-Ky.), a member of the Foreign Relations Committee, criticized Trump’s statement as promoting a “Saudi Arabia First” policy instead of an “America First” doctrine.

Paul has called for a vote on legislation that would block any arms sales to Saudi Arabia. Trump has valued the overall arms deal at $110 billion.