Ecuador and Peru signed the Brasilia Presidential Act peace agreement on October 26, 1998, which ended hostilities, and effectively put an end to the Western Hemisphere's longest running territorial dispute. The Guarantors of the Rio Protocol (Argentina, Brazil, Chile, and the United States of America) ruled that the border of the undelineated zone was to be set at the line of the ''Cordillera del Cóndor''. While Ecuador had to give up its decades-old territorial claims to the eastern slopes of the Cordillera, as well as to the entire western area of Cenepa headwaters, Peru was compelled to give to Ecuador, in perpetual lease but without sovereignty,  of its territory, in the area where the Ecuadorian base of Tiwinza – focal point of the war – had been located within Peruvian soil and which the Ecuadorian Army held during the conflict. The final border demarcation came into effect on May 13, 1999, and the multi-national MOMEP (Military Observer Mission for Ecuador and Peru) troop deployment withdrew on June 17, 1999.