Donald Trump and Vladimir Putin may have had more conversations during this month's G20 summit than the White House has acknowledged.

The president had at least two known conversations with his Russian counterpart, including one that was discovered this week, plus a brief handshake.

But Russian Foreign Minister Sergei Lavrov told NBC News that 'they might have met even much more than just three times.'

'Maybe they went to the toilet together – that was the fourth,' he snarked.

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Russian Foreign Minister Sergei Lavrov told NBC News that Donald Trump and Vladimir Putin may have had more encounters at this month's G20 summit than the three that are known

Lavrov compared a pre-summit anteroom to a kindergarten hallway where children chat as they're waiting for school to start, and joked the Trump and Putin could have visited the men's room together

Lavrov used the analogy of young children mingling at school.

'When you are bought by your parents to a kindergarten, do you mix with the people who are waiting in the same room to start going to a classroom?' he asked.

He added: 'I remember when I was in that position I did spend five or ten minutes in the kindergarten before they brought us to the classroom.'

Lavrov said that at the G20 there is 'a room where they get together before an event starts,' since 'they cannot arrive all at the same time on a bus.'

He also addressed this week's breathless reporting of G20 dinner chat between Trump and Putin.

'After the dinner was over ... I was not there ... President Trump apparently went to pick up his wife and spent some minutes with President Putin ... so what?' he said.

Russia's Foreign Minister Sergei Lavrov tells @KeirSimmons Trump and Putin may have had more meetings at G-20 summit https://t.co/m4lYVHQPTF — NBC News (@NBCNews) July 21, 2017

Trump and Putin had an official bilateral meeting during the summit in Hamburg, Germany, and that second, previously undisclosed meeting during the dinner for world leaders.

Trump has blasted the news coverage of that second meeting, tweeting Tuesday night: 'Fake News story of secret dinner with Putin is "sick." All G 20 leaders, and spouses, were invited by the Chancellor of Germany. Press knew!'

He added: 'The Fake News is becoming more and more dishonest! Even a dinner arranged for top 20 leaders in Germany is made to look sinister!'

The White House, in a statement, claimed it was only a 'brief conversation.'

Dinner table: The G20 leaders were not seated next to their spouses for the dinner on July 7, but after dinner Trump and Putin spoke privately

The official meeting: Trump and Putin had two hours of bilateral talks at the Hamburg summit on July 7

However the New York Times and the Washington Post both said the meeting went on for an hour.

The nature of the meeting - with no U.S. officials present to take notes - means that knowing what happened depends entirely on the president's recollection of events.

The undisclosed meeting could explain discrepancies between the Russian and U.S. versions of what they spoke about at the G20.

Trump tweeted on July 9: 'Sanctions were not discussed at my meeting with President Putin. Nothing will be done until the Ukrainian & Syrian problems are solved!'

Putin said subsequently that he had pressed for the return of Russian-owned diplomatic compounds that were seized by the Obama administration in retaliation for Russian election interference.

'Pretty much everyone at the dinner thought this was really weird, that here is the president of the United States, who clearly wants to display that he has a better relationship personally with President Putin than any of us, or simply doesn't care,' Ian Bremmer, president of the Eurasia Group, told The New York Times.

According to the White House Trump approached Putin and Melania at the end of the meal.

Trump blasted the coverage on Tuesday night in a tweet, saying it was 'sick'

He then attacked the broader media in the Twitter tirade

Trump had been seated between Akie Abe, wife of the Japanese prime minister, and Juliana Awada, wife of Argentinian president Mauricio Macri.

The White House said that each leader was only allowed one interpreter, and the U.S. translator spoke Japanese, not Russian, so the conversation with Putin used the Russian one.

In a statement, the White House said: 'The insinuation that the White House has tried to 'hide' a second meeting is false, malicious and absurd.'

It was unclear who had made such an insinuation but the White House had never disclosed the meeting in any form until Tuesday.

In fact it was Bremmer who revealed its existence in a newsletter to group clients of the Eurasia Group.

He also stood by his assertion that the White House had 'no intention' of disclosing the meeting using Twitter and also saying: 'Readout from Trump Admin on what was/wasn't discussed in official meeting w Putin useless when there was 1 hour convo off books that eve.'

The lack of information about the meeting at the time may partly be explained by the fact that press were stopped from watching the dinner before the food was served.

The dinner took place in a large room and a National Security Council spokesman told CNN that the hour-long talks between Trump and Putin did not take place in a private office.

First meeting: This was the scene of the very first encounter between Trump and Putin, just before the 'family photo' of G20 leaders was taken

News breaker: Russia expert Ian Bremmer revealed the second, post-dinner meeting and also said that the White House did not mean for it to become public

At the G20, the meeting between the U.S. and Russian presidents had always been the most-anticipated part of the event.

Trump in fact met Putin first unexpectedly behind the scenes, just before the 'family photo' of world leaders.

Putin was speaking to European Commission president Jean-Claude Juncker when Trump approached him and the two exchanged handshakes.

They then met after the Friday afternoon group photo for more than two hours, with Rex Tillerson, the Secretary of State, and Sergei Lavrov, the Russian foreign minister present, as well as a translator from each country.

What was agreed at the meeting became the subject of much contention afterwards.

There was a deal on a ceasefire in part of Syria which appeared to have been pre-arranged.

But on Sunday July 7, Trump tweeted to say: 'Putin & I discussed forming an impenetrable Cyber Security unit so that election hacking, & many other negative things, will be guarded.. ... and safe.'

The idea was roundly mocked and compared by Republican Russia hawk Marco Rubio to 'partnering with Assad on a "Chemical Weapons Unit", and appeared to be disavowed shortly afterwards.

Trump also said that 'questions were asked about why the CIA & FBI has to ask the DNC 13 times for their SERVER and were rejected'.

Putin himself offered an account of events shortly after the meeting.

The Russian leader said his Trump asked 'many questions' on election interference.

But he would not reveal details of his exchange with Trump, saying the conversation was confidential.

'He asked questions, I replied. It seemed to me that he was satisfied with the answers,' Putin said.