President Obama returned a formal military salute by saluting with a coffee cup he had in his hand as he stepped off his U.S. Marine Corps helicopter in New York on Sunday.

A video of the gesture that some are calling the “latte salute” was uploaded to the White House Instagram account.

“President Obama just landed in New York for #UNGA2014,” the caption reads.
 
The salute is “the most important of all military courtesies,” says a manual, titled “Customs and Courtesies,” for Marine Corps officer candidates, The Daily Caller reported.

 “In general, do not salute when… carrying articles with both hands or being otherwise so occupied as to make saluting impractical,” the manual says.

Mr. Obama did not appear to be carrying anything else in his hands when he made the unusual salute.

Reaction on social media was swift.

“Dear POTUS. Place cup in left hand and salute with the right. Please. You are embarrassing us,” one commenter said on the White House’s Instagram account.