Venezuela on Thursday vowed a "forceful response" if oil drilling begins in contested waters off neighboring Guyana, as announced by US oil giant ExxonMobil this week.

Caracas has long claimed the region of Essequibo -- which makes up about two-thirds of Guyana's territory -- but has amped up its rhetoric since its neighbor began issuing licenses for oil companies to operate there.

Venezuelan Defense Minister Vladimir Padrino wrote on X that while ExxonMobil may have the protection of the United States and Guyana, "in the maritime space that rightfully belongs to Venezuela, they will receive a proportional, forceful response that adheres to the law."

ExxonMobil -- which discovered the massive crude reserves off Guyana in 2015 -- announced Tuesday that it plans to drill two exploratory wells this year off the coast of Essequibo, which has been administered by Guyana for more than a century.

In December, Venezuelan President Nicolas Maduro called a controversial non-binding referendum that overwhelmingly approved the creation of a Venezuelan province in Essequibo, sparking fears of a military conflict in largely peaceful South America.

Tensions were further inflamed when Britain sent a warship to the area, prompting Maduro to mobilize 5,600 troops in military exercises near the border.

However tensions lowered after a meeting between the countries' foreign ministers in Brazil in January, following earlier face-to-face talks between Maduro and Guyana President Irfaan Ali, who agreed not to resort to force.

The border dispute is currently before the International Criminal Court (ICJ) in The Hague.

On Wednesday, Venezuela's Vice President Delcy Rodriguez accused ExxonMobil of seeking "to protect its illicit operations in a sea which is pending delimitation, under the war-mongering mantle of the United States in complicity with Guyana."