ABUJA, Sept 6 (Reuters) - The Economic Community of West African States (ECOWAS) will hold an extraordinary summit on Guinea on Thursday, according to a staff memo shared with Reuters. Special forces soldiers ousted long-serving President Alpha Conde and dissolved his cabinet on Sunday, prompting ECOWAS to demand a return to constitutional order and threaten to impose sanctions. read more An ECOWAS spokeswoman did not immediately reply to a request for comment late on Monday.