Turkish officials have said they feared Khashoggi was killed and dismembered inside the consulate. "They had come to kill him", the source said. Khashoggi is a critic of the Saudi government who has written about the country as a correspondent for the Washington Post.
Turkey has expressed concerns that Khashoggi could have been murdered inside the building, while the Saudi government has denied involvement in the case, claiming that the journalist disappeared after he left the consulate.
Mr. Trump also deflected any blame should Republicans lose the House of Representatives in November, saying that he was "helping people" with his campaign efforts and that he believes Republicans "going to do well". He said he has always been a staunch defender of Saudi Arabia on the Senate floor as a "good ally" of the United States.
A Turkish security official said no conclusive evidence emerged from the overnight search in the consulate.
Erdogan told journalists Tuesday that police sought traces of "toxic" materials and suggested parts of the consulate had been recently painted, without elaborating.
"We are strong and old allies".
Last night, a team of Turkish and Saudi officials entered the Saudi consulate in Istanbul for a joint inspection two weeks after Khashoggi went missing. They also noted apparent Saudi attempts to scrub the scene by bringing in cleaning crews and repainting areas of the consulate.
"Secretary Pompeo conveyed the importance of a conducting a thorough, transparent and timely investigation", said Heather Nauert, the State Department spokeswoman.More news: Tara Reid, Pooch Thrown Off Delta Flight After On-Board Disturbance
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Jonathan Fulton, assistant professor of political science at Zayed University in Abu Dhabi, said China had grown more serious in its regional arms relationships with Gulf states in recent years, with the potential to serve as a "wedge" as US-Saudi relations frayed. Khashoggi was a United States resident who wrote columns for the Washington Post and he was critical of the Saudi government, calling for reforms.
The disappearance and suspected murder of Jamal Khashoggi at the Saudi consulate in Istanbul has embarrassed Mohammed and strained relations with Washington.
Trump's warning drew an angry response Sunday from Saudi Arabia and its state-linked media, including a suggestion that Riyadh could wield its oil production as a weapon.
The president spoke with Saudi King Salman on Monday, who Trump said insisted he did not have any knowledge of what happened to Khashoggi.
Hours before they arrived, journalists photographed a cleaning crew entering the consulate with buckets, mops and what appeared to be cleaning solution.
In Istanbul, meanwhile, investigators entered the consulate for their own investigation. "It sounded to me like maybe these could have been rogue killers".
While the meetings were going on, Trump, in Washington, said on Twitter, "For the record, I have no financial interests in Saudi Arabia (or Russian Federation, for that matter)".
"Well this is not rogue killers, this is a rogue crown prince", Graham said in a separate interview with Fox News Radio.