A highly-complicated surgery to separate Moroccan Siamese twins will be performed tomorrow by a Saudi specialized medical team in Riyadh -based National Guard King Abdulaziz Medical City, it was reported here today. Dr. Abdullah Al-Rabee'a, head of the medical and surgical team, told Saudi Press Agency (SPA) that the operation for Safa and Marwa who reached Saudi Arabia coming from Morocco on April 4, 2008 on a special Saudi medical evacuation flight upon instructions of the Custodian of the Two Holy Mosques King Abdullah bin Abdulaziz Al Saud will start at 7:00 a.m. on Saturday and is expected to last for at least ten hours. Given the congenital complications at the heart of one of the twins, Marwa, and the fact that they share the liver and digestive system, are conjoined at the chest and abdomen and have incomplete lower abdomen wall, the success expectancy of the operation was reduced by the medical and health team to 60%, said Dr. Al-Rabee'a, citing that his team has so far performed 18, all successful, separation operations for multi-national patients.