The United States announced joint military flight drills in Guyana on Thursday as tensions over a contested oil-rich region with neighbor Venezuela prompted the U.N. Security Council to call an urgent meeting.

A border feud has been spiraling over the Essequibo region, which has been administered and controlled by Guyana for more than a century, although Venezuela also claims the disputed area. Venezuela recently conducted a referendum, which it claims citizens supported, that aims to give Venezuela authority over the Essequibo region. Guyanese officials said in response that the country is preparing to defend itself and its borders in case of an invasion.

The spat is drawing in the international community, with the U.S. announcement of military exercises the latest sign that Washington is alarmed at the threat from the authoritarian leftist Venezuelan government of President Nicolás Maduro.