Venezuelans vote in a referendum on Sunday to decide whether that country should create its own state within a large section of neighbouring Guyana
The move has been denounced by much of the international community and has been ruled invalid by the International Court of Justice.
Guyana has called the move a step towards annexation and raised concerns of a possible military conflict between the two South American nations.
The area in question, the densely forested Essequibo region, amounts to about two-thirds of Guyana's current territory and is roughly the size of Florida.
Venezuela has long claimed the land, which it argues was within its borders during the Spanish colonial period.
It dismisses an 1899 ruling by international arbitrators that set the current boundaries when Guyana was still a British colony.
The recent discovery of vast offshore oil fields in the region has heightened the stakes in the dispute.