The international sports tribunal on Thursday rejected an appeal by 67 Russian athletes seeking to overturn an IAAF doping ban on them competing at the Rio Olympics, reports AFP, from Lausanne (Switzerland). The ruling by the Court of Arbitration for Sport (CAS) is seen as a key indicator as the International Olympic Committee (IOC) debates whether to order a blanket ban on Russia over accusations of state-run doping. The IOC said it will study the CAS decision before a conference call on Sunday with its executive board. A decision on banning Russia from the Rio Games which start on August 5 could come this weekend, an IOC spokesperson said.