Beyoncé Knowles and Jay-Z are planning on getting married in the Caribbean next week, it has been claimed.The couple were overheard excitedly talking to record executives at NewYork's STK restaurant on Saturday about a special "four-day"celebration on a yacht in St. Barts to mark the rapper turning 37 on Monday. It has been suggested that the birthday bash is just a cover and insist Beyoncé, 25, and the hip-hop mogul - who have been dating for four years -are actually preparing to tie the knot. A source told the New York Post newspaper: "Beyoncé is throwing Jay afour-day birthday party, but it's really a wedding."Insiders say friends and family invited to the celebrations were told to have passport applications filed by last Friday, so they could witness the pair exchanging vows.The four-day party will begin on a luxury yacht before guests are ferried across to Anguilla for the wedding ceremony, which will take place at the five-star resort of Cap Juluca. Beyoncé and Jay-Z reportedly visited the exclusive venue earlier this year and decided it would be perfect for their big day.