Under mounting global pressure, Saudi Arabia has changed its narrative about Khashoggi's killing several times, only recently acknowledging that Turkish evidence shows it was premeditated.
Turkish officials say a "hit squad" of Saudi agents dispatched from the gulf killed Khashoggi in the consulate and dismembered his body before returning to Saudi soil.
Khashoggi, who had become a frequent critic of the crown prince of Saudi Arabia, was in the consulate to obtain papers for his planned marriage.
Saudi leadership has blamed a "rogue operation" for the killing of Khashoggi.
United States Defence Secretary James Mattis met Saudi Arabia's Foreign Minister Adel al-Jubeir and called for a transparent investigation into Saudi journalist Jamal Khashoggi's death while condemning the incident.
Khashoggi, a onetime Saudi insider and US resident who lived in self-imposed exile for nearly a year before his death, had written critically of the crown prince in columns for the Washington Post.
Khashoggi, 59, entered the Saudi consulate in Istanbul on October 2 to obtain paperwork necessary for his upcoming marriage to Cengiz, a Turkish national.
"Unfortunately, there has been this hysteria in the media before the investigation was complete", he said during a panel at the Manama Dialogue, which was organised by the International Institute for Strategic Studies in Manama, the capital of Bahrain.
The initial Turkish inquiry has concluded that the killing was premeditated, a fact Saudi officials have taken some time to acknowledge.
Cengiz said she had not been contacted by Crown Prince Mohammed or the Saudi Royal family, nor offered any condolences by them.
Turkish President Recep Tayyip Erdogan has said that a 15-person team came from Riyadh to kill Mr Khashoggi.
In a speech this past week, Erdogan called on Saudi Arabia to extradite any suspects for a trial in Turkey.
The article also claimed that the unnamed source confirmed that MI6 - British Secret Intelligence Service - had warned Saudi Arabian counterparts to cancel the mission but this request was ignored.
"If Khashoggi did, in fact, have proof that Saudi Arabia was deliberately misusing phosphorous for this goal, it would be highly embarrassing for the regime and provides the nearest motive yet as to why Riyadh may have acted when they did against him", he said. "I want to know the details of who is responsible".
Cengiz criticised the response to Khashoggi's death from some countries and singled out Donald Trump for criticism, saying she feared the U.S. president was "paving the way for a cover-up".
White House spokeswoman Sarah Sanders told a media briefing the administration was "weighing different options" and would make an announcement.
