WASHINGTON (WASHINGTON POST) - The United States received a payment of US$100 million (S$137 million) from Saudi Arabia on Tuesday (Oct 16), the same day Secretary of State Mike Pompeo arrived in Riyadh to discuss the disappearance of journalist Jamal Khashoggi, a State Department official confirmed.

Saudi Arabia publicly pledged the payment to support US stabilisation efforts in north-eastern Syria in August, but questions persisted about when and if Saudi officials would come through with the money.

The timing of the transfer, first reported by The New York Times, raised questions about a potential payoff as Riyadh seeks to manage the blowback over allegations that Saudi agents were responsible for Mr Khashoggi's disappearance.

The State Department denied any connection between the payment and Mr Pompeo's discussions with Saudi officials about Mr Khashoggi, a Washington Post contributing columnist.

"We always expected the contribution to be finalised in the fall time frame," Mr Brett McGurk, the State Department's envoy to the anti-Islamic State coalition, said in a statement. "The specific transfer of funds has been long in process and has nothing to do with other events or the secretary's visit."

Saudi Arabia, an oil rich monarchy and staunch US ally, has long relied on its financial largesse to persuade partners to support its foreign policy objectives. Western diplomats suspect that the kingdom will also compensate Turkey for its willingness to launch a joint investigation on Mr Khashoggi's disappearance - a payback that could come in the form of large-scale debt relief, strategic buyouts or other arrangements that boost Turkey's ailing economy.

Mr Khashoggi's disappearance has hurt the reputation of Saudi Arabia's Crown Prince Mohammed bin Salman, whose close relationship with President Donald Trump's son-in-law and senior adviser Jared Kushner has put him at the centre of the administration's Middle East policy.

Turkish authorities say Mr Khashoggi was killed on Oct 2 during a visit to the Saudi consulate in Istanbul to obtain a document required to get married.

Mr Trump initially promised "severe punishment" for Saudi Arabia if the US determined that Saudi agents killed Mr Khashoggi. But the president has since floated an alternative theory involving "rogue killers" and compared the case to the sexual assault allegations against recently confirmed Supreme Court Justice Brett Kavanaugh.

"Here we go again with you know you're guilty until proven innocent," Mr Trump told The Associated Press in an interview on Tuesday.

During Mr Pompeo's visit to Saudi Arabia, the top diplomat and the crown prince smiled for the cameras and emphasised the two countries' mutual interests. When asked if he had learnt any details about Mr Khashoggi's disappearance, Mr Pompeo told reporters:"I don't want to talk about any of the facts; they didn't want to, either, in that they want to have the opportunity to complete this investigation in a thorough way."

The Saudi payment to support stabilisation efforts in Syria is a cornerstone of Mr Trump's "America First" strategy, which calls on regional countries to take on a greater burden for security challenges, including Syria. In August, US officials hailed the Saudi pledge and said the US would use US$230 million earmarked to help stabilise Syria for other purposes.

Middle East experts said the timing of the transfer likely sent a clear message to the Trump administration.

"In all probability, the Saudis want Trump to know that his cooperation in covering for the Khashoggi affair is important to the Saudi monarch," said Professor Joshua Landis of the University of Oklahoma. "Much of its financial promises to the US will be contingent on this cooperation."

The Saudi Embassy in Washington did not respond to requests for comment.