President Donald Trump is one of the few US officials who refuses to criticize the Saudi crown prince and the Russian president for violating human rights.
Speaking in the White House before he left for the summit, Mr Trump tempered expectations. "I like the deal we have now".
The meeting between the two leaders comes a few months after it was announced that - following US's reimposition of sanctions against Iran - India will cut its oil imports from Tehran to zero.
The prince is accused of ordering the killing of Mr Khashoggi, who died in the Saudi consulate office in Turkey.
The killing of Khashoggi drew outrage across Western states and governments traditionally allied to Saudi Arabia have found themselves having to balance calls to punish the kingdom with the risk of souring ties and potentially jeopardising commercial and military contracts.
Despite the reassurances, Macron appears to reply "I am anxious", as the awkward encounter continued.
A cryptic exchange between the pair on Friday was caught on video and shared by the English-language Saudi Gazette.
In the audio of the conversation, it's possible to make out the prince saying "Don't worry", to which Macron responds: "I am worried".
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Later in the one-minute clip Macron says: "You never listen to me" and the crown prince replies: "I will listen, of course". Thank you." Macron: "I don't want. French President Emmanuel Macron has also said he will meet with the Saudi leader.
The embrace came amid reports that Russian Federation and Saudi Arabia have reached a pact to cut oil production when the OPEC cartel meets on December 6 in Vienna, to help shore up collapsing crude prices. With the latter conflict ongoing for more than three years, one wonders if in the past Macron hasn't been firm enough, or maybe the Saudi prince isn't quite as honorable as he claims.
Prince Mohammed and Russian President Vladimir Putin both grinned broadly and greeted each other with an enthusiastic, thumping handshake that resembled a high-five, and hearty laughter.
However, Russia has suggested USA domestic politics may have been the real reason behind the cancellation.
"They exchanged pleasantries at the leaders' session as he did with almost every leader in attendance", the White House official said on Friday.
Ms Merkel said she would address the Russia/Ukraine stand-off during their discussions, a crisis she has blamed "entirely" on Russia.
Separately, the arrival of German Chancellor Angela Merkel was delayed after her official jet was hit by technical issues, forcing it to return to the country shortly after take-off.
"It only wasn't set up", the president told reporters Thursday. Both the leaders are in Buenos Aires to attend the Group of 20 (G-20) summit which kicks off today (Friday).