R+B superstar Beyonce Knowles has become the new face of American Express, according to reports. The Irreplaceable singer - who already endorses products by Pepsi, L'Oreal and MCDonald's among others - will front the new advertising campaign for the financial giants, joining the likes of actors Robert De Niro and Kate Winslet, and sports stars Tiger Woods and Venus Williams. A source tells OK! magazine, "She's a role model for so many young people. She has tremendous cross-over appeal the same way Tiger (Woods) does. She's an inspiration for lots of people. She's a great fit for American Express."