CHISINAU, Feb 22 (Reuters) - President Vladimir Putin revoked on Tuesday a 2012 decree that in part underpinned Moldova's sovereignty in resolving the future of the Transdniestria region - a Moscow-backed separatist region which borders Ukraine and where Russia keeps troops. The 2012 decree committed Russia to seeking ways to resolve the separatist issue "based on respect for the sovereignty, territorial integrity and neutral status of the Republic of Moldova in determining the special status of Transdniestria". See here for a complete list of exchanges and delays