Ukrainian President Volodymyr Zelensky seems to have done some breathing exercises and cooled off after a heated exchange with President Trump in the Oval Office on Friday -- a headline-making moment around the globe.

In a lengthy message posted to social media on Saturday morning ... Zelensky acknowledged that lasting peace in Eastern Europe would be “difficult” without U.S. support ... and he gave props for America's help during Russia’s three-year invasion of his country.

The message had a vastly different feel and tone from the blowup the two world leaders had in the White House ... which was live around the globe.

Trump basically went off on Zelensky after a bilateral meeting became a total trainwreck in minutes ... all the while Vice President Vance needled Zelensky about not being grateful to the U.S. for all the country has provided during the war.

Zelensky meanwhile stood his ground ... defending his military and citizens, saying the U.S. has not directly experienced the consequences of the war -- a rebuttal that really pissed off the president.

Trump sternly replied ... “You don’t have the cards right now. With us, you start having cards" adding that Zelensky is “gambling with the lives of millions of people, you’re gambling with World War III ... and what you’re doing is very disrespectful to the country, this country, that’s backed you far more than a lot of people said they should have.”

In the end ... Trump kicked Zelensky outta the White House and a presser that was supposed to happen afterward was obviously canned.

Hopefully, both have counted to 10 ... and are ready to try critical meetings once again.