OSAKA, Japan – Three years after Russian efforts to influence the 2016 election triggered federal investigations, President Donald Trump asked Vladimir Putin on Friday not to do it again in 2020 – though he did so quickly and playfully.

"Don't meddle in the election, president," Trump said in a joking manner to Putin as cameras clicked and reporters shouted questions. Wagging a finger at the Russian president, Trump repeated, "don't meddle in the election."

When an interpreter translated Trump's "request," Putin laughed.

Later, a White House readout of the meeting said Trump and Putin discussed arms control, Iran, Syria, Venezuela and Ukraine – but said nothing about election interference.

G20:Trump arrives at G20 complaining about allies Germany, India and his host, Japan

Trump's light-hearted manner did not go down well with critics who accused him off laughing off a legitimate threat from an autocrat who has a grudge against the United States.

"Trump consistently appeases Putin at expense of US national security interests," tweeted Michael McFaul, an American ambassador to Russia during the Barack Obama administration.

It was yet another remarkable Trump-Putin moment, nearly a year after a landmark news conference in Helsinki in which Trump appeared to agree with Putin's denials that Russia interfered in the 2016 presidential election by hacking Democrats.

In Osaka, after a reporter asked Trump if he would tell Putin not to meddle in 2020, the president said, "Yes, of course, I will." He then turned to the Russian leader to make his joke.

'None of your business':Trump's own brand of diplomacy is on display at G20. How will it fare with Valdimir Putin, Xi Jinping?

The entreaty came after opening statements in which Trump said that "it's a great honor to be with President Putin," and that they would discuss issues like trade and nuclear disarmament. He said nothing at that point about election interference.

"We have a very very good relationship and we look forward to spending some very good time together," Trump said. "A lot of very positive things are going to come out of the relationship."

Putin, via a translator, said he was looking forward to the session with Trump.

"We haven't seen each other since Helsinki," he said.

Earlier in the day, Trump could be seen walking with Putin and gently patting him on the back just before the G-20 delegates posed for a group picture. Trump could also be seen amiably chatting up Saudi Crown Prince Mohammed bin Salman, who stood next to him for the photo.

This was the first face-to-face meeting between Trump and Putin since former special counsel Robert Mueller issued a report on Russian efforts to interfere in the 2016 presidential election in order to benefit Trump.

The Mueller report said Putin's government engaged in a sweeping plan to hack Democratic emails and push fake news about Trump opponent Hillary Clinton. It also said there was no evidence tying the Trump campaign to the Russian plot, but some aides welcomed Moscow's efforts to help them politically.

'It's unbelievable, OK?' Trump arrives at G20 complaining about allies Germany, India and his host, Japan

Democratic-run committees in the U.S. House are investigating aspects of Mueller's report, including allegations that Trump sought to obstruct justice and stop the investigation in its tracks.

Denying collusion and obstruction, Trump has said that Mueller and the Democrats are engaging in a political "witch hunt."

The Putin meeting highlighted a day at the G-20 in which Trump pretty much stayed on his best behavior, praising allies he had bashed in the run-up to the global conclave.

More:Trump arrives in Japan for G-20. What to expect from meetings with China's Xi Jinping, Russia's Putin

Days after criticizing them over issues like tariffs and mutual defense pledges, Trump told Japanese Prime Shinzo Abe, Indian Prime Minister Narendra Modi and German Chancellor Angela Merkel that he wanted to work with them on trade and economic development.

“The chancellor is a great friend of mine," Trump said of Merkel, with whom he has often been at odds.

Trump did seize the opportunity to mock Democratic presidential candidates as they held a debate in Miami.

In the midst of meetings with global leaders, Trump tweeted out an attack on Democratic candidates who expressed support for health care plans that would cover migrants who are in the U.S. illegally. Trump claimed this Democratic position would win him re-election.

"That’s the end of that race!" he tweeted.

At another point in the day, Trump passed up the chance to criticize Iran, saying he was confident he and allies would work out ways to calm tensions with the Tehran regime. At the same time, Trump added an implicit threat when he said that, hopefully, "it's going to work out" between the U.S. and Iran.

"If it does, great," he told reporters. "If it doesn’t, you‘ll be hearing about it.”

The Putin meeting dominated the day. Throughout Trump's presidency, critics have accused him of being too solicitous of Putin, and said the president appears to be grateful for Russia's election assistance.

At their last formal meeting, a July special summit in Helsinki, Trump expressed sympathy for Putin's denials about Russian meddling, appearing to take the Russian leader's word over the conclusions of the U.S. intelligence community.

Days later, Trump walked back his comments and said he did believe the intelligence assessment about Russia culpability.

Still, Trump sought to meet with Putin in the latter part of last year. They scheduled a meeting at a G-20 summit in November in Buenos Aires, but canceled it during a pivotal moment in the Mueller investigation – though Trump and Putin still wound up meeting briefly anyway.

Trump also wants to talk with Putin about a new agreement to control nuclear arms. Putin, meanwhile, is protesting U.S. plans to withdraw from the 1987 Intermediate-Range Nuclear Forces (INF) Treaty, a landmark nuclear arms control pact inked with the Soviet Union.

Trump has taken steps to conceal details of five previous meetings with Putin, another subject of an investigation by House Democrats. He has spoken to the Russian president alone, without aides or translators.

The Democratic-led House Oversight Committee is investigating reports that Trump destroyed interpreters' notes from his meeting with Putin at a G-20 summit two years ago in Hamburg, Germany. They are seeking any summaries or readouts of Trump-Putin meetings.

As Trump prepared to meet with Putin again on Friday, a group of Democratic lawmakers back in Washington, D.C., expressed support for legislation designed to protect election security from foreign interference.

Senate Minority Leader Chuck Schumer, D-N.Y., said Trump needs to look Putin "in the eye" and tell him that "America will not tolerate interference" in the U.S. political system.

"But sadly," he said, "if past is prologue, the American people will have little confidence that President Trump will stand up to Vladimir Putin."

As he arrived in Osaka for the G-20, Putin told the Financial Times that the "liberal idea" of government is dead, and he cited immigration policy as an example.

Putin said Merkel made "a cardinal mistake" in admitting more than a million refugees to Germany, and praised efforts by Trump to stem the flow of migrants into the United States from Mexico and Central America.

As for Trump himself, Putin told the Financial Times the president is "not a career politician" and is responsive to his constituents.

"I do not accept many of his methods when it comes to addressing problems," Putin said. "But do you know what I think? I think that he is a talented person. He knows very well what his voters expect from him.”