One day we will reach a point where entire business etiquette courses are taught solely using footage of US President Donald Trump trying to shake the hands of world leaders.

This time, the US President was meeting his Polish counterpart, President Andrzej Duda, in Warsaw, before his attendance at the G20 Summit in Germany, which begins on Friday.

However, it was Trump's attempted handshake with Duda's wife, Polish first lady Agata Kornhauser-Duda, which has attracted attention.

Footage appears to show Trump extending his hand to Kornhauser-Duda, a high school teacher, who walks straight past it to greet his wife, Melania Trump.