MOSCOW — President Donald Trump tweeted Thursday that he has canceled a scheduled one-on-one meeting with Russian counterpart Vladimir Putin at the G-20 summit in Argentina.

The tweets came as Trump was en route to Buenos Aires. The pair had been scheduled to hold discussions in private at the summit on Saturday before being joined by other government officials, Kremlin aide Yuri Ushakov told the TASS state news agency late Wednesday.

Trump's tweets also came about an hour after he told reporters the meeting would "probably" happen as he left the White House.

"We haven’t terminated that meeting. I was thinking about it, but they’d like to have it. I think it's a very good time to have the meeting," he said.

Trump said he would make up his mind after getting a report on the latest developments on Russia's conflict with Ukraine on Air Force One.

"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" with Putin, he wrote in a pair of tweets. "I look forward to a meaningful Summit again as soon as this situation is resolved!"

The scuttling of the sitdown comes after Russian forces sparked an international crisis by attacking and seizing three Ukrainian vessels that were trying to pass through the Kerch Strait, a narrow artery that connects the Black Sea to the Sea of Azov.

Eleven Russian vessels surrounded Ukraine's two light military ships and one tugboat, ramming them before eventually opening fire on Sunday, Ukrainian President Petro Poroshenko told NBC News.

Poroshenko insists his country is under "extremely serious" threat of a land invasion, and that's why he had to declare martial law for 30 days in regions adjacent to Russia.

Nikki Haley, the outgoing U.S. ambassador to the United Nations, and Secretary of State Mike Pompeo joined other Western leaders in immediately pointing the finger of blame at the Kremlin and Putin.

However, Trump said Monday, "We don't like what's happening either way.”

Putin and Trump had been expected to discuss disarmament, global anti-terrorism and future bilateral relations, Ushakov told TASS.

Putin spokesman Dmitry Peskov echoed that on Thursday, telling reporters: "Bilateral relations-connected issues will come first. We should give thought to how to start discussing bilateral relations, strategic security and disarmament, and regional conflicts.”

The cancellation also came hours after former Trump Organization lawyer Michael Cohen pleaded guilty to making false statements to Congress about a proposed project to build a Trump Tower in Moscow during Trump's presidential campaign.

Trump already has much to discuss with global leaders in the Argentinian capital, and will have a working dinner with Chinese President Xi Jinping on Saturday night.

His last encounter with Putin drew international criticism in July after he chose to side with the Russian president against American intelligence agencies over whether Moscow meddled in the 2016 election.

Elena Holodny reported from Moscow, and Alastair Jamieson from London.