UNITED NATIONS, United States (AFP) — UN Secretary General Antonio Guterres on Monday appointed a new envoy to resolve a border dispute between Venezuela and Guyana, saying he was ready to turn to the International Court of Justice to settle the issue.

The dispute, which dates from the early 19th century, began heating up in 2015 after a significant oil find was announced in an offshore concession granted by Guyana that Venezuela claims is in disputed waters.

Caracas has laid claim to waters off the Essequibo, a disputed territory that borders Venezuela and encompasses more than half of Guyana.

Dag Halvor Nylander of Norway was appointed to help broker a settlement “until the end of 2017, with a strengthened mandate of mediation,” UN spokesman Stephane Dujarric said.

If no progress is made toward a settlement by the end of 2017, Guterres “will choose the International Court of Justice as the next means of settlement,” he added, “unless the governments of Guyana and Venezuela jointly request that he refrain from doing so.”