In tweets sent from aboard Air Force One, Trump said he was doing so because Russia had not returned the Ukrainian boats and sailors it seized after accusing them of illegally entering Russian waters near Crimea.
Later, White House press secretary Sarah Sanders told reporters aboard Air Force One that before canceling the meeting with Putin, the president consulted with Secretary of State Mike Pompeo, National Security Adviser John Bolton and Defense Secretary James Mattis. She said she did not know if Trump had called Putin.
Trump's tweets came shortly after news broke that his former personal attorney, Michael Cohen, had pleaded guilty to making false statements to Congress last year about how long he had pursued building a Trump Tower project in Moscow, including during the 2016 presidential campaign, and who he told about that. Trump called Cohen a "liar" and said there was nothing wrong in pursuing the project during the campaign.
Just a short time before sending the tweets, as he left the White House, Trump told reporters his planned meeting with Putin at the G-20 was still on and that it would “probably” be happening.
But he also said he would be getting a finalized report during his flight about Russia’s recent seizure of Ukrainian vessels.
“I probably will be meeting with President Putin," Trump said as he headed to his helicopter." We haven't terminated that meeting. I was thinking about it, but they'd like to have it,” Trump said. “I think it’s a very good time to have the meeting. I'm getting a full report on the plane as to what happened with respect to that and that will determine what I am going to be doing.”