Jamal Khashoggi: What we know about the journalist's disappearance/ AFP
President Donald Trump has vowed to "get to the bottom" of the case of missing Saudi journalist Jamal Khashoggi
Trump told reporters he had talked to the Saudi authorities "at the highest level" about Mr Khashoggi.
Mr Khashoggi, a US resident and critic of the Saudi monarchy, entered the Saudi consulate in Istanbul on 2 October and has not been seen since,reports BBC.
Turkish authorities say Mr Khashoggi was killed. Saudi Arabia denies this.
"We cannot let this happen to reporters, to anybody," Mr Trump said on Wednesday.
"We're demanding everything. We want to see what's going on there."
The White House said Secretary of State Mike Pompeo and senior officials had spoken to Saudi Crown Prince Mohammed Bin Salman on Tuesday and asked for more details about the situation.
Both Turkey and Saudi Arabia are allies of the United States.
Earlier on Wednesday, Turkish media outlets published CCTV footage which they say shows evidence of a plot linked to Mr Khashoggi's disappearance.
It shows purported Saudi intelligence officers entering and leaving Turkey via Istanbul airport.