Venezuela claims Essequibo has historically been considered part of its territory since 1777, when it was part of the Spanish empire, with the Essequibo river forming a natural boundary. AFP

The foreign ministers of Guyana and Venezuela are due to meet on Thursday in Brazil to discuss the simmering crisis on their border over a disputed oil-rich region.

With both sides holding firm, observers do not expect a major breakthrough to address the root of the disagreement: Venezuela's claim to the Essequibo region that makes up about two-thirds of Guyanese territory.

Thursday's meeting was called after Venezuelan President Nicolas Maduro and his Guyanese counterpart Irfaan Ali ruled out resorting to force at a crisis summit in Saint Vincent and the Grenadines last month.

Essequibo has been administered by Guyana for over a century and is the subject of border litigation before the International Court of Justice (ICJ) in The Hague -- whose jurisdiction in the matter Venezuela rejects.

The region is home to 125,000 of Guyana's 800,000 citizens, but Caracas has long claimed the region should be under its control.

The squabble was revived in 2015 after US energy giant ExxonMobil discovered huge crude reserves in Essequibo and it reached fever pitch last year after Georgetown started auctioning off oil blocks in the region.

Maduro's government then called a controversial, non-binding referendum which overwhelmingly approved the creation of a Venezuelan province in Essequibo, sparking fears of a military conflict.

Ivan Rojas, a Venezuelan international relations professor, told AFP no solution is likely to emerge from Thursday's meeting.

"It is likely they will simply focus on mutual assurances and keeping the peace."

The dispute escalated dramatically last month with joint US-Guyana military exercises, followed by the arrival of a British warship in Guyanese waters and a "defensive" Venezuelan military deployment in response.

On Wednesday, Guyana said it remained "fully committed" to the agreement struck with its neighbor in December, "in particular the maintenance of peace."

President Ali told AFP in Georgetown that the meeting was an important step towards fulfilling the December agreement, which foresees the creation of a commission "to look at all the consequential matters."

The ministers would also seek to set up another presidential meeting.

"It gives us now the opportunity to outline the agenda with items that both sides would want to speak on... issues of trade, climate, energy security, initiatives to expand our trade," the president said.

Venezuela's Foreign Minister Yvan Gil, who will be meeting his counterpart Hugh Todd, described the dialogue as a "success for diplomacy."

On his arrival in Brasilia, Gil told the state broadcaster VTV the meeting "removes any possibility of conflict beyond the territorial controversy we have."

For his part, Maduro said last month: "We believe in diplomacy, dialogue and peace."

Brazil, which has common borders with both countries and is acting as mediator, welcomed the "engagement of Guyana and Venezuela in the ongoing dialogue process" in a statement announcing Thursday's meeting.

Venezuela claims Essequibo has historically been considered part of its territory since 1777, when it was part of the Spanish empire, with the Essequibo River forming a natural boundary.

Former British and Dutch colony Guyana, however, says the border was ratified in 1899 by an arbitration court in Paris.