President George Vella, who is currently in New York, has laid flowers on the 9/11 memorial.
He also had talks with Miguel Ángel Moratinos, United Nations Under-Secretary-General and High Representative for the United Nations Alliance of Civilisations, at UN headquarters.
The President's Office said they discussed the geo-political situation globally and the threats it is posing to multilateralism.
President Vella is accompanied by Home Affairs Minister Byron Camilleri.
On Sunday he visited the Maltese community at the Malta Centre in Astoria.