Yet, a Kremlin spokesman said Friday that Putin and Trump would hold a brief, impromptu meeting at the summit, even as the White House continued saying there was no scheduled meeting.
Putin was accused in September by Britain's security minister of being "ultimately responsible" for the alleged attempt in May by Russian intelligence officers to murder former Russian double agent Sergei Skripal and his daughter in England with a nerve agent.
And for years before that, a number of Putin's critics have died from violence or other under unusual circumstances.
While the CIA has "high confidence" that Crown Prince Mohammed ordered Khashoggi's murder, Trump has given the crown prince — who denies doing so — the benefit of the doubt, saying last week that "maybe he did and maybe he didn't!"
The president also has recently praised Saudi Arabia for falling oil prices even as outrage continues over the murder of Khashoggi, a resident of the United States who contributed to The Washington Post.
In July, Trump sparked outrage at a news conference in Helsinki, when he likewise sided with Putin, who was standing next to him, over American intelligence agencies who say Russia meddled in the election.
"My people came to me, (Director of National Intelligence) Dan Coats came to me and some others. They said they think it's Russia. I have President Putin. He just said it's not Russia. I will say this, I don't see any reason why it would be," Trump said.
The since-deceased Sen. John McCain, R-Ariz., said at the time that Trump's joint news conference with Putin was "one of the most disgraceful performances by an American president in memory."
"The damage inflicted by President Trump's naivete, egotism, false equivalence, and sympathy for autocrats is difficult to calculate," McCain said.