The US has asked Turkey for a recording said to provide strong evidence that missing Saudi journalist Jamal Khashoggi was killed at the Saudi consulate in Istanbul.

“We have asked for it, if it exists,” President Donald Trump told reporters at the White House.

Mr Khashoggi has not been seen since entering the building on 2 October. Saudi Arabia denies killing him.

Mr Trump denied he was trying “to cover” for Saudi Arabia.

Meanwhile, the Washington Post has announced that it will publish the last column Mr Khashoggi wrote before his disappearance on the importance of a free press in the Middle East.

What is Trump’s latest position?

Saudi Arabia is one of Washington’s closest allies and the Khashoggi disappearance is putting the administration in an awkward position.

Confirming that the tape has been requested, Mr Trump added: “I’m not sure yet that it exists, probably does, possibly does.”

• What we know about Saudi journalist’s disappearance
• Did Apple Watch record Khashoggi killing?

Mr Trump said he expected a report from Secretary of State Mike Pompeo who has just been to Saudi Arabia and Turkey.

The president said the truth would come out “by the end of the week”.

He rejected suggestions he was trying to provide cover for Saudi Arabia: “No, not at all, I just want to find out what’s happening.”

Over the past few days, Mr Trump has raised the possibility of “rogue killers” being behind the journalist’s disappearance. And he has cautioned against rushing to blame Saudi leaders, telling the Associated Press news agency that they were being treated as “guilty until proven innocent”.

What is reported to be on the recording?

The existence of audio evidence that Mr Khashoggi – a critic of Saudi leaders – was murdered was revealed by Turkish investigators early on in their inquiries.

Reports in Turkish media give gruesome details of what are said to be his final minutes.

A Turkish newspaper says the consul himself, Mohammed al-Otaibi, can be heard in the audio recording of Mr Khashoggi’s death.

Yeni Safak, which is close to the government, quotes him as telling alleged Saudi agents sent to Istanbul: “Do this outside. You’re going to get me in trouble.”

Mr Otaibi flew back to Riyadh on Tuesday.

How is Turkey’s investigation progressing?

Early on Thursday, investigators were seen leaving the Saudi consul’s residence, about 200m (650ft) from the consulate, following a search that lasted almost nine hours, according to Reuters news agency.

The team included prosecutors and forensics experts in white overalls.

The search had been expected to take place on Tuesday, but it was delayed because the consul’s family were still inside, Turkish Foreign Minister Mevlut Cavusoglu said.

Several vehicles with Saudi diplomatic number plates were filmed by CCTV cameras moving from the consulate to the residence just under two hours after Mr Khashoggi entered the consulate on the day he vanished.

The consulate building was searched on Monday.

Mr Cavusoglu said his meeting with Mr Pompeo had been a “beneficial and fruitful” encounter. The US secretary of state had talks with President Recep Tayyip Erdogan, too.

On Tuesday, Mr Pompeo was in Riyadh for talks with Saudi Arabia’s King Salman and Crown Prince Mohammed bin Salman, who he said “strongly denied” any involvement in the journalist’s disappearance.

• Why Saudi Arabia matters to the West
• Donald Trump and a world of disorder

The events of 2 October

Mr Khashoggi is a US resident and columnist for the Washington Post newspaper who went into self-imposed exile last year after reportedly being warned by Saudi officials to stop criticising the crown prince’s policies.

He arrived at the consulate at 13:14 local time for an appointment to obtain paperwork so he could marry his Turkish fiancée.

Saudi officials have insisted Mr Khashoggi left the consulate soon afterwards and came to no harm.

But Turkish officials believe an assault and struggle took place in the building.

• The journalist who vanished into a consulate
• Is this the end of Saudi prince’s honeymoon?
• Why Khashoggi case alarms Saudi activists

They allege that Mr Khashoggi was killed by a team of Saudi agents who were pictured entering and leaving Turkey on CCTV footage released to media outlets.

The New York Times reports that four of the 15 agents have links to Crown Prince Mohammed, while another is a senior figure in the country’s interior ministry.

On Tuesday, G7 foreign ministers called for Saudi Arabia to conduct a “transparent” investigation into the issue.

Meanwhile, International Monetary Fund chief Christine Lagarde has become the latest high-profile figure to withdraw from a major Saudi investment conference next week following Mr Khashoggi’s disappearance.