The US Senate has passed a resolution stating Crown Prince Mohammed bin Salman is responsible for the killing of journalist Jamal Khashoggi.
The move is a direct rebuke to the Saudi Arabian royal and calls for the country's government to "ensure appropriate accountability".
It is also a rare challenge to Donald Trump, who has remained neutral on who is to blame for Mr Khashoggi's death and has repeatedly praised the kingdom.
In one instance, he suggested that "maybe the world should be held accountable because the world is a vicious place".
The bipartisan vote came two months after the journalist's death at the Saudi consulate in Istanbul on 2 October. Mr Khashoggi, a prominent journalist who wrote for The Washington Post, was a fierce critic of the Saudi rulers.
US intelligence officials have previously concluded that Mohammed bin Salman must have at least known of the plot to kill Mr Khashoggi.
The resolution also came after senators passed a separate measure calling for the end of US aid to the Saudi-led war in Yemen.
Senators voted 56-41 to recommend that the US stop supporting the conflict.
Frustration with the crown prince and the White House prompted several Republicans to support the Yemen resolution as a way to rebuke the long-time ally.
Others already had concerns about the war, which human rights groups say is wreaking havoc on the country and subjecting civilians, many of them children, to deadly disease and indiscriminate bombing.
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Independent Senator Bernie Sanders, who co-sponsored the Yemen resolution with Republican Senator Mike Lee, called the vote a "historic moment".
Mr Sanders said by acting, the Senate was making clear "that the constitutional responsibility for making war rests with the United States Congress".