U.S. President Donald Trump on Thursday said he was canceling a meeting with Russian President Vladimir Putin scheduled to take place during the upcoming summit for the Group of 20 industrialized nations in Argentina, citing renewed tensions between Russia and Ukraine.

"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. I look forward to a meaningful Summit again as soon as this situation is resolved!" Trump tweeted after departing for the G20 summit.

Trump's tweet was a sudden turnaround. Roughly an hour earlier, he had told reporters he would probably meet with Putin at the summit and said it was "a very good time to have the meeting."

But Trump had also said he would get a final report during the flight to Argentina on the tension in the region after Russia seized Ukrainian vessels near Crimea on Sunday.

Differences over Ukraine, as well as Moscow's role in the war in Syria, have been an irritant in U.S.-Russian relations for years.

The administration of former President Barack Obama imposed sanctions on Russia for what it calls the reunification of Crimea from Ukraine in 2014. That in part brought ties between Washington and Moscow to their lowest point since the end of the Cold War.

Since then, the United States has investigated Russia's possible interference in the 2016 presidential election that Trump won. Russia has denied meddling and Trump has repeatedly said there was no collusion.