Saudi Arabia on Sunday called the killing of journalist Jamal Khashoggi at its Istanbul consulate a "huge and grave mistake", but sought to shield its powerful crown prince from the widening crisis, saying Mohammed bin Salman had not been aware.
In an interview with the Washington Post, Trump said that "obviously there's been deception, and there's been lies".
The report by pro-Government daily Yeni Safak alleges the Crown Prince telephoned the Washington Post columnist moments before he was killed in the Saudi consulate in Istanbul earlier this month.
"Their stories are all over the place", added Mr Trump. He adds Saudi officials do not know the whereabouts of Khashoggi's remains.
Saudi Arabia said 18 Saudi suspects were in custody and intelligence officials had been fired.
The announcement on Sunday by Turkish President Recep Tayyip Erdogan that he will "go into detail" about the Khashoggi case in a speech in parliament heightened hopes for some clarity in a case that has been shrouded in mystery, conflicting accounts and shocking allegations since Khashoggi, a critic of Prince Mohammed bin Salman, disappeared after entering the consulate on Oct 2.
Erdogan and Trump also discussed bilateral relations, the presidential press office said in a statement.
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But a series of U.S. lawmakers of both parties expressed doubt, demanding a stronger stance against the longtime U.S. regional partner.
"First of all, their explanation is insultingly stupid", he told Fox News' Chris Wallace during an interview Sunday, flabbergasted by "the idea that this guy walked in the room with 15 security people, got in a fight and was accidentally killed and then they happened to have apparently an ability to dismember him and get rid of him that happened to be there".
After Saudi Arabia confirmed his death, she wrote on Twitter in Arabic: "They have taken your body from this world, but your handsome smile will stay in my world forever". Trump added that he has yet to be shown any evidence by intelligence officials that would make him believe MBS had any direct role. Nobody has told me he's not responsible. "We're going to go into detail", he said. Amid Trump's apparent equivocations, several key Republicans demanded a tougher stance. Bob Corker (R-Tenn.) said Sunday on CNN's "State of the Union", referring to the crown prince.
"Do I think he did it?" South Carolina Sen. Lindsey Graham said Sunday "I find it impossible to believe that the Crown Prince was not involved. I haven't heard either way", the president said.
California Rep. Adam Schiff, the top Democrat on the House intelligence committee, said on ABC's "This Week" that the killing should be a "relationship-altering" event for the USA and Saudi Arabia, which has said it will retaliate against any economic sanctions or other moves against it.
"This behaviour is outside the norm to the point that the people involved need to be removed in my view". King Salman, 82, has handed the day-to-day running of Saudi Arabia to him. "I'm willing to separate the two", he continued, accusing the prince of acting in a "barbaric fashion".
"This was an operation where individuals ended up exceeding the authorities and responsibilities they had", he said.
"We're trying to ascertain the facts as to what happened in the consulate", he said.