PRAGUE — On the top floor of an opulent Art Deco building in the heart of old Prague, the new lord mayor was standing with a glass of sparkling wine in hand, greeting diplomats as they made their way into his official residence for a New Year’s gathering.

But when the Chinese ambassador reached Mayor Zdenek Hrib, the diplomat was not in a celebratory mood.

“He demanded that I kick out the representative of Taiwan,’’ Mr. Hrib recalled of the confrontation last January. “I said, ‘We do not kick out our guests.’”

As the line of people backed up, with other ambassadors urging the Chinese representative to move on, he grew more and more incensed until, finally, he stormed out.