Trump added that he hoped to have “a meaningful Summit again as soon as this situation is resolved!”

“Based on the fact that the ships and sailors have not been returned to Ukraine from Russia, I have decided it would be best for all parties concerned to cancel my previously scheduled meeting in Argentina with President Vladimir Putin,” Trump wrote while flying on Air Force One en route to the summit.

The announcement, which Trump made on Twitter , came roughly an hour after the president told reporters the meeting would “probably” go ahead as planned.

The Kremlin said it did not receive advance notice of the cancellation, with Putin spokesman Dmitry Peskov telling Russian news outlets they learned of the news from Trump's tweets.

Before departing the White House on Thursday morning, Trump said it was a “very good time” to meet with Putin despite Russia's recent seizure of Ukrainian ships and sailors off the coast of Crimea.

“I probably will be meeting with President Putin. We haven't terminated that meeting. I was thinking about it, but we haven't. They'd like to have it,” the president said.

But Trump noted he would be receiving a “full report” aboard Air Force One on the naval incidents and said that “will determine” whether the meeting would go ahead as planned.

Trump first cast doubt about the meeting on Tuesday in an interview with The Washington Post, citing Russia's actions that have triggered international condemnation and enflamed the long-running conflict with Ukraine.

The seizures marked the first armed confrontation between Russia and Ukraine since the Kremlin's occupation in Crimea in 2014 and the aggressive actions raised the possibility of a response from NATO and the United Nations.

But the Kremlin said Thursday morning that the White House confirmed plans for the meeting and announced it would occur on Saturday morning on the sidelines of the G-20 in Buenos Aires, Argentina.

Bolton told reporters on Tuesday the two leaders were expected to touch on the Middle East, arms control and security issues in “a continuation of their discussion in Helsinki.”

Trump's meeting with Putin last summer in the Finnish capital was widely panned by lawmakers and U.S. allies for his failure to publicly confront the Russian leader over Moscow's interference in the 2016 election.

The Putin meeting was set to be one of the most closely watched sit-downs for Trump at the G-20.

Trump is also scheduled to meet with Chinese President Xi Jinping for a high-stakes discussion on trade and will huddle with Turkish President Recep Tayyip Erdoğan, who is expected to pressure Trump over the killing of Saudi journalist Jamal Khashoggi.

Updated 12:47 p.m.