evidence: Leaders of Guyana and Venezuela to meet this week as region worries over their territorial dispute [...] The dispute over Essequibo, which represents two-thirds of Guyana and borders Venezuela, worsened after Venezuela’s Dec. 3 referendum on claiming sovereignty over the region located near massive oil deposits. Venezuela maintains Essequibo was within its boundaries during the Spanish colonial period, and rejects the border drawn by international arbitrators in 1899, when Guyana was under British rule. Venezuelan officials also argue that a 1966 agreement between their country, Britain and the colony of British Guiana effectively nullified the original arbitration.