Hollywood star Angelina Jolie showed off her newly-adopted Vietnamese son in a British magazine Wednesday, describing him as "very strong" and saying he was slowly adapting to his new life.

Pax Thien, aged three, is pictured playing by a swimming pool and in bed with Jolie's two other adopted children, Maddox, aged five, and two-year-old Zahara.

"He is a very serious, very sweet little boy," Jolie told Hello! magazine in an interview.

"We are slowly beginning to build his trust and bond but it will feel complete only when we are all a family.

"You can imagine what courage it takes to be in all new surroundings with new people and a new language. He is very strong.

"It will take him a while to realise he has a family; that his new life is permanent and it won't keep changing."

Jolie, who is building a "rainbow family" with partner Brad Pitt, said she had given the child a Gameboy as one of his first presents.

"He has never had anything to call his own," she added.

The 31-year-old screen star last week used a private plane to travel to Ho Chi Minh City, where she picked up the boy from an orphanage, and on to Hanoi where she arrived Monday.

She has now left Vietnam for the United States after the boy was granted a visa.