Kill Bill star Lucy Liu is calling on Americans to pay $1 (50 pence) for tap water in restaurants to help save children's lives in Africa. Liu, a United Nations Children's Fund (Unicef) ambassador, has just returned from Cote d'Ivoire in Africa, where she witnessed the threat to child survival caused by a lack of clean drinking water. And now the actress is encouraging people to pay for the tap water they'd normally get for free during World Water Week this week (begs17Mar08) - to help raise $1 million (GBP500,000) to provide African children with purified water. Liu says, "If you go to a restaurant and they'd give you tap water for free, they're asking you to donate a dollar for the tap water. "One dollar will provide water for 40 children for one day, which is incredible. It's kind of great - you get to go out and enjoy food with people and you get to give back in such a small and simple way." More than 2,000 restaurants across the U.S. have signed up to participate in World Water Week.