Secretary of State Mike Pompeo participated in the meeting, the State Department said.
Khashoggi was last seen alive entering the Saudi consulate October 2.
Riyadh finally accepted yesterday what Turkey had said virtually from the start - that he was killed in a premeditated hit. USA intelligence officials and lawmakers as well as the European Union have said that an operation targeting a critic of the royal court in a foreign country is unlikely to have been ordered without the knowledge of senior Saudi officials.
Turkish officials especially are pushing the Saudi government to identify who ordered the killing. It was not clear what could be heard.
"We have shared with those who sought additional information some of the information and findings that the prosecutor has allowed us to share", Turkish Foreign Minister Mevlut Cavusoglu told reporters, without giving details.
"This was a very, very painful incident for all Saudis and everybody else on the planet", he said of the Khashoggi killing.
How Western allies deal with Riyadh will hinge on the extent to which they believe responsibility for Khashoggi's death lies directly with the prince and the Saudi authorities.
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"The chancellor urged Saudi Arabia to ensure a rapid, transparent and credible investigation".
What U.S. President Donald Trump called "one of the worst cover-ups in the history of cover-ups" was revealed to the world by Turkish leaks of information, including references to purported audio recordings of the killing, and security camera footage of the Saudi officials who were involved as they moved around Istanbul.
Salah Jamal Khashoggi and his uncle Sahl bin Ahmed Khashoggi were received Tuesday by Saudi King Salman and Crown Prince Mohammed bin Salman, who expressed their condolences over the killing of the dissident journalist.
"From this place where Jamal lost his life, we clearly state that we will not accept compromises in the case of his murder", said a statement from the group, read by Ayman Nour, the Egyptian chief of opposition broadcaster El-Sharq.
In his first public comments on the matter, bin Salman promised on Wednesday that the killers would be brought to justice.
In another sign that the kingdom is seeking to contain the widespread fallout, Salah Khashoggi, the eldest son of Jamal Khashoggi, has left Saudi Arabia, two people close to the family said Thursday.
A state media photo showing Salah staring coldly at the prince as the pair shook hands went viral on social media, where rights activists demanded the immediate lifting of the travel ban.