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.