US Secretary of State Mike Pompeo is to meet Saudi King Salman amid growing controversy over the fate of Saudi journalist Jamal Khashoggi.
He will later visit Turkey, where Mr Khashoggi was last seen at the Saudi consulate in Istanbul two weeks ago.
Turkish officials believe Mr Khashoggi was murdered by Saudi agents but Riyadh has always strongly denied this.
On Monday, President Donald Trump suggested “rogue killers” could be behind Mr Khashoggi’s disappearance.
The president provided no evidence to back his comment, but said that during a phone call the Saudi King had firmly denied knowing what had happened to Mr Khashoggi.
Early on Tuesday, Turkish police left the Saudi consulate where Mr Khashoggi was last seen after an overnight search.
It was the first time they had been allowed to enter the building since the journalist’s disappearance following disagreements between the two sides over the terms of any search.
However, unconfirmed reports in the US media suggest Saudi Arabia is preparing to admit that Mr Khashoggi died as a result of an interrogation that went wrong and that the original intention had been to abduct him.
Meanwhile, Arabic channel Al-Jazeera quotes Turkey’s attorney-general’s office as saying it has found evidence to back claims that Mr Khashoggi was killed inside the mission.
The issue has strained Saudi Arabia’s ties with its closest Western allies.
- Did Apple Watch record Khashoggi killing?
- Why Saudi Arabia matters to the West
- What we know about Saudi journalist’s disappearance
- Donald A Turkish security source has told the BBC that officials have audio and video evidence proving Mr Khashoggi was murdered inside the building.Trump and a world of disorder
A Turkish security source has told the BBC that officials have audio and video evidence proving Mr Khashoggi was murdered inside the building.
How are the Saudis reacting?
Diplomatic pressure is growing on the Saudis to give a fuller explanation.
On Monday, King Salman ordered an investigation into the case.
“The king has ordered the public prosecutor to open an internal investigation into the Khashoggi matter based on the information from the joint team in Istanbul,” an official quoted by Reuters news agency said.
The official said the prosecutor had been instructed to work quickly.
- The journalist who vanished into a consulate
- Why Khashoggi case alarms Saudi activists
Last week, Turkey accepted a Saudi proposal to form a joint working group to investigate Mr Khashoggi’s disappearance.
On Sunday, Riyadh angrily rejected political and economic “threats” over the case of the missing journalist and said it would respond to any punitive action “with a bigger one”.
How was the consulate search conducted?
Investigators entered the building in Istanbul on Monday afternoon – first a Saudi team followed roughly an hour later by Turkish forensic police.
Turkish diplomatic sources had said the consulate would be searched by a joint Turkish-Saudi team.