SCO serves something of a counterweight to American-Europe alliance, despite being more loosely organized. Pakistan also wants membership in SCO. China is concerned that troubles between India and Pakistan might fracture the organization. A fractured SCO will be ineffective at its intended purposes. However, excluding Pakistan and India will also restrict the potential of SCO, that potential being the biggest economic-military cooperation pact in the world. I think China will keep delaying the matter until Pakistan and India can settle their differences sufficiently.