Relations between the United States and Saudi Arabia cannot progress until Crown Prince Mohammed bin Salman is "dealt with," Sen. Lindsey Graham said on Saturday during a visit to Turkey, NBC News reported.

The South Carolina Republican has become a fierce critic of the kingdom's de facto ruler since the murder of journalist Jamal Khashoggi in October. Graham's latest comments come as tensions in the region run high amid U.S. plans to withdraw troops from Syria.

"What has transpired over the [last] couple of years has been unnerving to say the least," Graham said about the crown prince's leadership. "Taking all of your critics and throwing them in prison, the brutal murder [of] Mr. Khashoggi in Turkey, violating every norm of international behavior."

Khashoggi, a Washington Post columnist and critic of Prince Mohammed, was killed by a team sent from Riyadh after he entered the Saudi Consulate in Istanbul on Oct. 2. Saudi authorities have acknowledged that the killing was premeditated, but blamed it on rogue operatives. His body has not been found.