Trump said in a tweet he won't meet the Russian president in Buenos Aires, due mainly to the ongoing tensions related to Russia's detention of three Ukrainian naval ships last weekend.
"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," he wrote.
"I look forward to a meaningful Summit again as soon as this situation is resolved!"
The Kremlin said it didn't have any other information about Trump canceling the meeting.
"If this is so, [Putin] will have a couple of additional hours on the program for useful meetings on the sidelines of the summit," a spokesman told state-run news agency TASS.
White House press secretary Sarah Sanders said Monday Trump and Putin would meet in Buenos Aires Saturday -- and Kremlin spokesman Dmitry Peskov told reporters earlier Thursday the meeting was still on.
"Washington has confirmed. ... This is in the interests not only our two countries, but the world at large," Peskov said.
Russia seized the Ukrainian ships and crew in the Kerch Strait on Sunday. Putin said they entered territorial waters illegally to provoke a response. That led Ukrainian President Petro Poroshenko to declare martial law in some parts of his country for 30 days.
Russia has said that response was political, meant to boost Poroshenko's standing ahead of Ukrainian elections. Poroshenko called the ships' captures acts of aggression.
"It is a provocation initiated by the current authorities, and I think by the [Ukrainian] president, in light of the upcoming elections to be held next year," Putin told an audience at an investment forum in Moscow, CNBC reported. "The incident in the Black Sea happened, it is a border incident, no more."
Tensions in the region toward Russia have been strained since 2014, when Moscow annexed Crimea -- a move many in the international community don't formally recognize.