Describing the disappearance as a "terrible thing", Trump said the U.S. would find out what happened to Khashoggi.
'We encourage joint Saudi-Turkish efforts in that regard, and expect the Saudi Government to provide a complete and detailed response'.
The statement went on to say that Saudi Arabia is "committed to its principles, rules and traditions and is in compliance with worldwide laws and conventions".
Saudi Arabia rejected threats to punish it over the disappearance of journalist Jamal Khashoggi in Istanbul, saying the kingdom would retaliate against any sanctions with tougher measures, the official state news agency said on Sunday.
"For sure, they listened to the conversation between me and Jamal and other activists, in Canada, in the States, in Turkey, in Saudi Arabia", Omar Abdulaziz said in an interview with the Canadian Broadcasting Corporation.
Saudi journalist and Washington Post contributor Khashoggi vanished after entering the consulate to obtain documents for his upcoming marriage.
"None of us know what happened, but we are all extremely concerned about the stories that have emerged, and the country that can help us get to the bottom of this is Saudi Arabia", he added.
Risks for global financial stability have risen
Khan said he will present a roadmap before the nation listing steps the government will take to stabilise the economy. President Donald Trump's America First trade policy.
The Turkish leadership has so far stopped short of accusing Saudi Arabia, although pro-government media have published sensational claims, including that an "assassination team" was sent to Istanbul to kill Khashoggi.
"He also stressed the Kingdom's keenness on the interest of its citizens at home and overseas and its keenness in particular to clarify the whole truth about the disappearance of the citizen Jamal Khashoggi", the SPA said. US officials say they are seeking answers from the Saudi government and are not yet accepting the Turkish government's conclusions.
The Saudi government has described the allegations as "baseless", but have offered no evidence that Mr Khashoggi left the consulate.
A joint statement of condemnation, if it is confirmed that Mr Khashoggi was killed by Saudi agents, is also being discussed by U.S. and European diplomats.
"That was our first hope, our first hope was that he was not killed, but maybe that's not looking too good... from what we're hearing", Trump told journalists at the White House.
US lawmakers have also called for economic sanctions to be imposed on the regime, sending the Saudi stock market down as much as seven percent in early trade on Sunday.
Trump defended a $110 billion arms deal he announced with Riyadh past year, insisting that the deal was worth 450,000 jobs inside the US.
"The kingdom affirms its total rejection of any threats and attempts to undermine it, whether through economic sanctions, political pressure or repeating false accusations", the kingdom's statement said.