The incident was captured on camera by a television crew from Nightline whom Hayek allowed accompany her on the goodwill trip in September.
The 42-year-old actress, who was nursing her own daughter Valentina at the time, offered to help when the baby's mother stopped producing milk.
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"The baby was perfectly healthy, but the mother didn't have milk. He was very hungry. I was weaning Valentina, but I still had a lot of milk that I was pumping, so I breast-fed the baby. You should have seen his eyes. When he felt the nourishment, he immediately stopped crying," Hayek said.