Transcript for Trump, Putin's high-stakes G-20 meeting
It was an historic first meeting. President Donald Trump coming face to face with Russian president Vladimir Putin at the g20 summit. After months of scrutiny over his friendliness toward Russia and speculation of Russian meddling in the U.S. Election, after an over two-hour closed-door discussion the two world leaders emerged with a momentous announcement. Here's ABC's Cecilia Vega. It's an honor to be with you. Reporter: The president reaching out to shake the hand of the man accused of meddling in America's election. I'm delighted to be able to meet you personally, Mr. President. Reporter: In their first face to face iwas president trump who made the first move with cameras capturing the smiling and the small talk, even a back pat. Then it was down to business. We're going to have a talk now. And obviously, that will continue. But we look forward to a lot of very positive things happening for Russia, for the united States. Reporter: When the doors closed, the white house says president trump addressed the big controversy head on, out of the gate raising concerns about Russia's meddling in the 2016 campaign. Though just a day earlier he still refused to fully accept U.S. Intelligence that Russia was to blame. Nobody really knows. Reporter: Secretary of state Rex tillerson, who's known Putin for years, was in that room. The president pressed president Putin on more than one occasion involving Russian involvement. President Putin denied such involvement, as I think he has in the past. Reporter: But after Putin asked for proof tillerson says the discussion was tabled. I think, again, the president's rightly focused on how do we move forward from what may be simply an intractable disagreement at this point. Reporter: The Russians tell a different story. Tillerson's counterpart sergei lavrov was in that room too. He claims trump heard Putin's denial and accepted it. The white house says that is not the case. After more than two hours of talks both sides agreed it is time to move on. So it seems that there was nothing that was going to be a consequence of any of those election interferences. That's a win. Reporter: Trump and Putin did manage to find some common ground on Syria, where the U.S. And Russia have clashed for years. The leaders announcing a new agreement with the help of Jordan for a cease-fire in southwest Syria. A cease-fire has been entered into. And I think this is our first indication of the U.S. And Russia being able to work together in Syria. Reporter: Both sides said the festering crisis dominated the discussion. Past cease-fire deals have been short-lived. But despite few details about how this one might be different, some see it as reason for hope. I think in today's meeting it seemed like you were having grown-ups discussing important foreign policy issues. That will be very reassuring to the people meeting for the g20 for the days to come. Reporter: In Moscow Russians viewed the meeting as a positive. It seemed like they established some personal contact and they seem quite alike. Friendly between themselves. They might find good decision for countries as well. Reporter: But overshadowed by that putin-trump meeting today, another major face to face, the president sitting down with Mexico's Enrique Pena Nieto. Do you still want Mexico to pay for the wall? Absolutely. Reporter: Not far from those meetings the demonstrations roared. Protesters being hosed down with water cannons. I don't think the three fascists who arrived yesterday have the right to be in my city, namely trump, Putin and erdogan. Reporter: While inside officials described the warmest meeting between an American and Russian leader in years. Putin and trump described as having positive chemistry. This meeting went on more than four times longer than it was supposed to. At one point someone sent first lady Melania trump inside to find out what was going on to try to get them to wrap up and they went on for another hour after that. Later cameras capturing these images of the first lady chatting and smiling with Vladimir Putin, seated right next to him for dinner. Could it be a trump-putin budding bromance? It looks like a very friendly meeting. This was a lot of patting and a lot of handshakes, and it was all very jolly. It suggests that Putin's approach to dealing with trump is much more that he wants trump to feel very good about that relationship. He doesn't want trump to feel in any way bruised or slighted by the way Putin's treating him. Reporter: Other American presidents have tried to make nice with soviet leaders, and it didn't go so well. John F. Kennedy's first meeting with Nikita khrushchev in 1961 famously went badly. When John F. Kennedy met with Nikita khrushchev at exactly this point in his presidency, khrushchev just had him for lunch and Kennedy said afterwards this was the worst day of my life. Reporter: This time the stakes for Russia are high. Already under sanctions for invading Ukraine and meddling in the U.S. Election, congress preparing to do more. While in Poland this week the president also turned up the heat. We urge Russia to cease its destabilizing activities in Ukraine and elsewhere and its support for hostile regimes including Syria and Iran. Reporter: But even as they sat down for that first meeting, questions about possible collusion during the campaign loomed large. Trump himself has offered mixed messages about whether he's met Putin before. I have no relationship with Putin. I don't think I've ever met him. I never met him. I don't think I -- You would know it if you did, wouldn't you? Yeah, I think so. So I don't think I've ever met him. Reporter: But he's also told a very different story. Not once -- Vladimir Putin have you ever met the guy? I met him once. Reporter: Not twice. Putin even sent me a present. Beautiful present. Reporter: At least three different times. I was in Moscow recently and I spoke indirectly and directly with president Putin. Reporter: Today both men made clear that handshake was a monumental step and both signaled there could be many more to come. The president hasn't been bashful about his interest in working with Russia. I like that Putin called me brilliant. They said you should disavow what Putin of Russia said. I said I'm not disavowing that he called me a genius. Are you crazy? Wouldn't it be nice if we could actually get along with Russia? Putin has been preparing for this meeting his whole life. Putin reads that he will get more out of the relationship with trump if he presents it as a broadly positive relationship. Reporter: Even some in the president's own inner circle privately raised concern about the optics of a cozy trump-putin relationship. There were those sharply scrutinized photos of that chummy oval office meeting with top Russian diplomats the day after the president fired his FBI director James Comey. The president, who has insisted the allegations of collusion with the Kremlin are fake news, shows no sign of allowing any of that controversy to get in his way in building new bridges with Russia. For "Nightline" I'm Cecilia Vega in Hamburg, Germany.
This transcript has been automatically generated and may not be 100% accurate.