Brad Pitt and Angelina Jolie are adopting a Vietnamese boy for son Maddox.

The 'Mr. and Mrs. Smith' stars - parents to five-year-old Cambodian son Maddox, two-year-old Ethiopian daughter Zahara and ten-month-old biological daughter Shiloh - believe an Asian boy would be the best addition to the family for Maddox.

A source says : "The process that began shortly after Shiloh was born last May.

"It's wonderful that people are excited about it. But Angelina is only at the beginning of a very comprehensive and detailed process."

Vietnamese adoption official Vu Duc Long revealed last week Angelina has filed papers to become an adoptive single parent to a boy between the ages of three and four from the Tam Binh orphanage on the outskirts of Ho Chi Minh City.

Long revealed the adoption process should not take more than three months.

Angelina filed for the adoption in the US and her application was approved by Long's department office last week.

It will now be sent to officials in Ho Chi Minh City, who will also review it.

Brad and Angelina made a surprise visit to the Tam Binh orphanage at Thanksgiving to give presents to the children.

Angelina said: "It would be good to balance the races so there's another African person in the house for Z and another Asian person in the house for Mad."