President Donald Trump has vowed to “get to the bottom” of the case of missing Saudi journalist Jamal Khashoggi.
Mr 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.
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.
What else does the video show?
Broadcast by Turkey’s TRT World channel and apparently obtained from security cameras, the footage shows vehicles driving up to the consulate, including black vans thought to be central to inquiries.
Groups of men thought to be Saudi are seen entering Turkey via Istanbul airport, checking in at hotels and later leaving the country.
Turkish investigators are looking into two Saudi Gulfstream jets that landed at the airport on 2 October. The video shows aircraft waiting on the tarmac.
Mr Khashoggi was visiting the consulate to finalise his divorce so he could marry his fiancée, Hatice Cengiz.
He is seen on the video entering the consulate while she waits outside.
Turkey’s Sabah newspaper reports that it has identified 15 members of an intelligence team it says was involved in the Saudi’s disappearance. Among them was a forensics expert, it says.
Turkey says it will conduct a search of the Istanbul consulate, while Saudi Arabia’s foreign ministry said the country was “open to co-operation” and a search of the building could go ahead.
How Turkey is tightening the screw
By Mark Lowen, BBC News, Istanbul
With every day, leaks from the Turkish investigation are drip-fed to the media here – and hope that Jamal Khashoggi might still be alive fades further.
A government source has told me President Recep Tayyip Erdogan is sounding more cautious than the leaks, because if he were to echo the allegations that Mr Khashoggi was murdered, it would mean kicking out the Saudi ambassador and consul general by now.
So the Turks are giving the Saudis a little breathing room to put forward their argument, while releasing bits of incriminating information to tighten the screws. So far, I’m told, the Saudis haven’t been co-operating – hence Ankara releasing the names of the alleged Saudi hit squad on Wednesday.
There are plenty of gruesome rumours flying around over what happened to Jamal Khashoggi. Saudi Arabia still insists it’s all baseless. But this is not simply one side’s word against the other. It’s video evidence, photos and intelligence against a claim of innocence so far not backed up.
Who is Jamal Khashoggi?
A critic of the crown prince, Mr Khashoggi was living in self-imposed exile in the US and writing opinion pieces for the Washington Post before his disappearance.
A former editor of the al-Watan newspaper, he was for years seen as close to the Saudi royal family. He served as an adviser to senior Saudi officials.
Media captionJamal Khashoggi: Saudi Arabia needs reform, but one-man rule is “bad” for the kingdom
But after several of his friends were arrested, his column was cancelled by the al-Hayat newspaper and he was allegedly warned to stop tweeting, Mr Khashoggi left Saudi Arabia for the US.
Last week, the crown prince told Bloomberg News that his government was “very keen to know what happened to him”, and that Mr Khashoggi had left “after a few minutes or one hour”.