Guyana's Ministry of Foreign Affairs accused Venezuela on Monday of posing a "threat to regional peace and security" with a recent decree extending its territorial claims farther out into the Atlantic Ocean.
The decree is a "flagrant violation of international law and is inconsistent with the principle that all states should respect the sovereignty and territorial integrity of other states," the ministry said in a statement Monday.
Guyana said any attempt by Venezuela to enforce its claims will be "vigorously resisted" and brought to the attention of the international community.
Venezuela has long claimed about two-thirds of Guyana west of the Essequibo River. Last month, the government of President Nicolas Maduro announced it was expanding its "integral maritime zone" farther out into the Atlantic Ocean in waters claimed by Guyana, clearly encompassing an area where Exxon Mobil Corp. reported that it had made a significant oil discovery.
The decree came a week after Exxon Mobil Corp., exploring under an agreement with Guyana, announced the discovery about 120 miles (about 193 kilometers) off the country's coast and was working to determine the commercial viability of the find.
In October 2013, the Venezuelan navy detained an oil research vessel operating under contract for U.S.-based Anadarko Petroleum Corp. because it claimed it was conducting exploration in its waters without authorization. Guyana had said the vessel was operating in its territory.