Macri has said in a letter to the U.N. Published yesterday that Argentina's government believes Malcorra is "amply" capable of filling the world body's top diplomatic post.
Malcorra is a former U.N. Undersecretary-general and chief of staff to Secretary-General Ban Ki-moon, whose term ends Dec. 31. She left the U.N. In December after Macri tapped her to be foreign minister.
The secretary-general is chosen by the 193-member General Assembly on the recommendation of the 15-member Security Council.
A group of 56 nations has been lobbying for the United Nations to have its first female chief.