The Trump administration has refused to respond to a request from Congress to provide a report determining who killed the Saudi journalist Jamal Khashoggi.
Senators wrote in October demanding the murder be investigated and that the White House give more information.
An administration official said the president was within his rights to decline to act.
Khashoggi was killed after entering the Saudi consulate in Istanbul in October last year.
He was a strong critic of the Saudi government. His body was reportedly dismembered and has still not been found.
US intelligence officials have reportedly said such an operation would have needed the approval of Crown Prince Mohammed bin Salman.
And on Saturday Baroness Helena Kennedy, member of a UN team of international experts who visited Turkey to investigate the murder, told the BBC the murder was planned at the highest level.
But Saudi officials insist he was murdered by a “rogue” team of Saudi agents not acting on the prince’s orders.
An administration statement said Mr Trump “maintains his discretion to decline to act on congressional committee requests when appropriate”.
However, Democratic senators told the New York Times the president was in breach of the so-called Magnitsky Act, which requires a response within 120 days to requests from Senate committee leaders. That deadline passed on Friday.
Timeline: Jamal Khashoggi’s deathHow the story unfolded
2 October 2018
Jamal Khashoggi enters the Saudi consulate in Istanbul. His fiancée Hatice Cengiz waits outside, but Khashoggi doesn’t emerge.
4 October 2018
In its first statement, Saudi Arabia says Khashoggi disappeared after leaving the consulate, and that it is trying to establish what happened to him.
6 October 2018
Khashoggi’s employers, the Washington Post, report that Turkish intelligence believe he was killed inside the consulate by a 15-man team sent from Saudi Arabia.
10 October 2018
CCTV footage showing the alleged hit squad arriving in Turkey is aired by Turkish media.
13 October 2018
Saudi Arabia attacks “lies and baseless allegations” and repeats it did not kill Khashoggi. The BBC learns Turkey has an audio recording indicating he was killed in the consulate.
15 October 2018
Donald Trump speaks to Saudi King Salman, who denies his country killed Khashoggi. Trump suggests “rogue killers” may be responsible.
20 October 2018
For the first time, Saudi Arabia admits Khashoggi is dead, claiming he died in a fight. This is met with wide scepticism. Two senior Saudi officials are fired.
22 October 2018
Saudi Arabia gives a new account, denying reports that Crown Prince Mohammed bin Salman ordered the killing, saying Khashoggi was murdered in a “rogue operation”. Footage emerges of a body double leaving the Saudi consulate dressed in Khashoggi’s clothes.
16 November 2018
The Washington Post reports the CIA has concluded Mohammed bin Salman ordered the killing. Trump later contradicts this, saying the CIA did not conclude the crown prince was responsible.
22 November 2018
France, like Germany and the UK, bans all the Saudi suspects from its territory. Germany also stops arms sales to Saudi Arabia.
Secretary of State Mike Pompeo has written to Senate leaders describing actions taken against individuals.
However, the documents do not indicate who was responsible for Khashoggi’s death, as demanded by the senators.
The US has imposed sanctions on 17 Saudi officials, including Saud al-Qahtani, a former adviser to the crown prince who, it alleged, was “part of the planning and execution of the operation” that led to Khashoggi’s murder.
But Mr Trump has faced criticism from senators for failing to condemn the crown prince directly.
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