The billboard picturing Melania Trump about to make a speech in front of the American flag was accompanied with the phrase, "Just imagine how far you can go with a little bit of English".
It was part of a marketing campaign by private English language school Americki Institut, which tried to persuade Croats to learn English by reminding them of the Slovenian-born US first lady's personal experience.
But Mrs Trump did not accept what was apparently meant to be a joke.
