Maggie Cheung was appointed UNICEF ambassador in China in Beijing on Thursday.

The Hong Kong actress said she immediately accepted UNICEF's offer to be an ambassador.

"I was very lucky on my career path," Cheung said. "Sometimes I couldn't help but wonder, why me? Why not somebody else to enjoy this luck? Now I understand. It's because I can sit here today to do some good things."

Cheung will lend her fame to become an advocate for the most poor and vulnerable children. She said she hoped to cover every place in China.

Earlier this year, she traveled with Yin Yin Nwe, a UNICEF representative, to Yunnan to visit children and women who lived in communities that have been hit hard by HIV and AIDS.

"One day we had afternoon tea with dozens of young infected women and their children there," Cheung said. "They told their stories. Suddenly a woman began to cry. Then we couldn't help but cry. I said: 'It's a good thing for us women to cry out.' So we wept for the whole time."

Every 10 minutes, a Chinese person is infected with HIV, Nwe said, adding that the disease is beginning to enter the main population and infecting women and children at a high speed. The infection rate for women has also risen sharply, from 19 percent in 2000 to about one third in 2009.