President Donald Trump on Wednesday criticized Ukraine President Volodymyr Zelensky amid their ongoing back-and-forth over settling the roughly three-year-long Russia-Ukraine war that Trump called a "killing field."

The most recent spat appears to have been sparked by Zelensky telling the Wall Street Journal that Ukraine will not legally recognize Russia's occupation of Crimea and part of U.S.-proposed peace plan. 

"This statement is very harmful to the Peace Negotiations with Russia in that Crimea was lost years ago under the auspices of President Barack Hussein Obama, and is not even a point of discussion," Trump posted on Truth Social.

He then said that "nobody is asking Zelensky to recognize Crimea as Russian territory," while also asking why Ukrainians didn't "fight for it eleven years ago when it was handed over to Russia without a shot being fired?"

Crimea is a peninsula in Eastern Europe and a former autonomous republic of the Soviet Union that was later a region of Ukraine. In 2014, Russia annexed Crimea, which is surrounded by the Black Sea.