Mediation efforts of Argentina, Brazil, Chile and the United States paved the way for the opening of diplomatic conversations that ultimately led to the signing of a definitive peace agreement (the Brasilia Presidential Act) on 26 October 1998. The peace agreement was followed by the formal demarcation of the border on 13 May 1999 and the end of the multi-national MOMEP (Military Observer Mission for Ecuador and Peru) troop deployment on 17 June 1999 which effectively put an end to one of the longest territorial disputes in the Western Hemisphere.