No other US officials were present and the pair communicated through a Russian translator meaning only the Kremlin has a record of what was said.
The head of the widely-respected Brookings Institute think tank has said the President could be “compromised” by the meeting.
The conversation came hours after Trump and Putin’s first official face-to-face meeting on July 7, which was originally scheduled to last just half an hour but stretched on for more than two.
The two world leaders were also captured on video shaking hands and exchanging a few words after they arrived at the G-20 summit of industrialised and developing nations earlier that day, reports the Associated Press.
White House spokesman Sean Spicer and National Security Council spokesman Michael Anton confirmed that Trump and Putin spoke at a dinner for world leaders and their spouses at the Group of 20 summit in Hamburg, Germany.
Anton would not specify the duration of the conversation. But he said the discussion was casual and should not be characterised as a “meeting” or even a less formal, but official, “pull-aside.”
“A conversation over dessert should not be characterised as a meeting,” he said.
Jason Kandar, a former US Army intelligence officer implied the circumstances of the meeting would have been favourable for a Russian President seeking to destabilise the US.
The dinner, hosted by German Chancellor Angela Merkel, was open only to world leaders and their spouses, as well as one translator per couple, according to a senior White House official who described the event on condition of anonymity despite the president’s criticism of unnamed sources.
The official stressed that Trump spoke with many leaders over the course of the dinner and said he spoke briefly with Putin, who was seated next to first lady Melania Trump, as the event was concluding. T
rump spoke with Putin using Russia’s translator, since the American translator did not speak Russian.
But Ian Bremmer, who said he spoke with two people who attended the dinner, said that Trump and Putin spoke for nearly an hour while sitting among the other world leaders and their spouses at the dinner. Bremmer is a foreign affairs columnist and the president of the Eurasia Group, a consulting firm.
Attendees described the meeting as startling, said Bremmer, who was told Trump was very animated as he spoke with Putin, often using his hands to gesture.
Trump defended the dinner in a pair of angry tweets late Tuesday that noted the dinner had been on his public schedule.
Trump and Putin’s relationship has been under scrutiny since the election campaign, when Trump repeatedly praised Putin as a strong leader and publicly encouraged him to hack then-rival Hillary Clinton’s emails. Trump aides have since said he was joking.
U.S. intelligence officials have concluded that the Russian government meddled in the 2016 election in order to help Trump. Trump has repeatedly cast doubt on their findings and dismissed investigations into potential collusion between his campaign and Moscow as a “witch hunt.”