BUENOS AIRES, Argentina - (AP) -- President Donald Trump abruptly canceled a planned meeting with Russian President Vladimir Putin as he headed to the Group of 20 Nations summit Thursday, citing Russia's seizure of Ukrainian vessels as a source of tension in a relationship he has fostered in the face of criticism.
Trump tweeted his decision from Air Force One shortly after his former lawyer, Michael Cohen, revealed he had lied to Congress to cover up that he was negotiating a real estate deal in Moscow on Trump's behalf during the Republican presidential primary in 2016.
The news ensured any meeting with Putin would spotlight the special counsel's investigation into whether the Trump campaign colluded with Moscow during the campaign. Trump has denied any wrongdoing and on Thursday called Cohen a "weak person" looking for a reduced sentence.
The last-minute move kicked off a global economic meeting expected to be dominated by Trump's seat-of-his-pants diplomacy. The Putin meeting -- a continuation of a controversial summit between the two in July -- was just one of a series of high-stakes items on Trump's agenda, which also includes talks with Chinese President Xi Jinping on how to ease a rising trade war.
Although Trump had previously floated canceling the meeting with Putin, White House spokeswoman Sarah Huckabee Sanders told reporters he did not make the final decision until boarding the plane for Argentina and speaking with national security adviser John Bolton and Secretary of State Mike Pompeo. The Kremlin said it had not been formally notified of the decision, which came hours after Moscow said the meeting was on track.
"I look forward to a meaningful Summit again as soon as this situation is resolved!" Trump tweeted from Air Force One.
Ukrainian President Petro Poroshenko praised Trump on Twitter, saying, "This is how great leaders act!"
Sanders also said two of Trump's planned bilateral meetings -- with Turkish President Recep Tayyip Erdogan and South Korea's Moon Jae-in -- had been canceled. Trump will instead speak informally with those leaders at the conference. She did not offer any explanation for those changes to the schedule.
The stakes for the sit-down between Putin and Trump were raised this week by Russia's stepped-up aggression in the Kerch Strait, stemming from its years long occupation of Eastern Ukraine. Russia recently seized three Ukrainian vessels and crews. Russia said Ukraine didn't have permission to pass between Russia's mainland and the Crimean Peninsula. Ukraine insisted its vessels abided by maritime laws.
Tensions had already been high over the war in Syria and allegations of Russian meddling in the 2016 presidential race. Trump has sought to improve the relationship with Putin, but was roundly criticized after the July summit in Helsinki for failing to publicly denounce Russia's interference and appearing to accept Putin's denials of such activity.
While Trump's statement was strongly worded, he has made similarly dramatic moves before only to walk them back. In the spring he canceled a planned summit with North Korea's Kim Jong Un, only to revive the meeting a week later.
The G-20 meeting in Buenos Aires comes amid growing economic uncertainty and global displeasure with Trump's trade policy.
The most pressing issue on Trump's packed schedule of meetings is whether he can reach a detente with Xi over trade after months in which both sides have raised tariffs on hundreds of billions of dollars of each other's goods, shaking financial markets and threatening the global economy. Without an agreement, the U.S. is set to increase the tariffs on January 1.
Departing the White House Thursday, Trump said he was "very close" to a deal with China, but added, "I don't know that I want to do it, because what we have right now is billions and billions of dollars coming in to the United States in the form of tariffs or taxes."
With China, experts said Trump likely wants to see something come out of the meeting.
"I think it's in President Trump's interest to have this meeting be viewed as a success," said David Dollar, a senior fellow in the John L. Thornton China Center at the Brookings Institution. "The markets are looking for some kind of dialing down of the rhetoric, and in particular markets are hoping there will not be an escalation of U.S. tariffs on January 1. So there's a foundation for some kind of agreement."
That approach leaves open the possibility for a preliminary or vague deal. Trump's Singapore summit with Kim produced a vague agreement on denuclearization with few, if any, specifics. Since then progress between the two nations appears to have slowed, but Trump continues to hail the meeting as a historic breakthrough.
Trump's advisers have sought to manage expectations heading into the talks, though some have projected optimism.
"If China will come to the table, or in this case the dinner table, with some new ideas and some new attitudes and some new cooperation, as the president said, there is a good possibility they could make a deal," economic adviser Larry Kudlow said this week. "He's open to it. So nothing is written in cement or stone."
On the ground for just two days, Trump is packing every moment with diplomacy, conducting bilateral meetings with numerous world leaders as well as group events.
Trump's visit will also put him in the same room as Saudi Arabian Crown Prince Mohammed bin Salman for the first time since the murder of journalist Jamal Khashoggi. The U.S. resident and prominent critic of the Saudi royal family was brutally killed last month upon entering the country's consulate in Istanbul, Turkey, a plot that sparked a diplomatic row that cast the future of the U.S.-Saudi relationship into doubt.
U.S. intelligence officials have concluded that the Saudi crown prince, known as MBS, must have at least known of the plot. Lawmakers in both parties have called on Trump to, at minimum, avoid the young heir apparent as punishment.
But Trump publicly announced his decision to effectively give the prince a free pass in the name of "America First," citing vastly exaggerated claims of Saudi military contracts and investments in the United States. The president also views Saudi Arabia as a vital counterbalance to Iranian influence in the Middle East.
While no official sit-down is scheduled, Trump has kept the door open to a casual meeting.
"I don't know that he's going to be there," Trump said last week. "But if he is, I would."
The crown prince arrived in Argentina on Wednesday and on Tuesday White House press secretary Sarah Sanders said, "I wouldn't say that we've ruled out any interaction."
Taking office on an "America First" platform, Trump has long had an uneasy relationship with his position on the world stage and has largely eschewed taking on a moral leadership role. Instead he has tailored his portfolio to promote American interests and to sow disruption. He has slapped tariffs on the European Union and pulled the U.S. out of the landmark Paris Climate Accord and the Iran nuclear deal. Trump also has suggested he might be willing to pull the U.S. out of NATO if member counties don't significantly boost their defense spending.