US President Donald Trump's handshake is under scrutiny again.

This time, Polish First Lady Agata Kornhauser-Duda appears to snub the US leader in Warsaw.

After shaking hands with Polish President Andrzej Duda, Mr Trump turns to shake Ms Kornhauser-Duda's hand, but she stretches out her hand for First Lady Melania Trump instead.

Ms Kornhauser-Duda then doubles back to shake Mr Trump's hand.

The snub was not intentional, but a clip of the awkward encounter has made its rounds on the Internet.

Mr Trump's body language, in particular his handshakes, have often been in the spotlight.

They range from a seemingly interminable clasp with Japanese Prime Minister Shinzo Abe, an apparent refusal to shake German Chancellor Angela Merkel's hand during their first meeting and a handshake that turned into a contest of wills with French President Emmanuel Macron.

On his second trip to Europe as president, Mr Trump flew to Hamburg on Thursday (July 6) to attend a summit of leaders of Group of 20 developed nations.

He affirmed the US commitment to the defence of Nato allies on Thursday in a Warsaw speech in which he said Western civilization must stand up to "those who would subvert and destroy it".