The United States, Mexico and Cuba aim to sign an agreement determining territorial water limits before U.S. President-elect Donald Trump takes office on Jan. 20, three diplomatic officials familiar with the matter said.
The accord will cover the Eastern Gap of the Gulf of Mexico, an area believed to be rich in oil and gas deposits. The three countries' overlapping claims in the Eastern Gap had created what is known as a "Doughnut Hole".
Trilateral discussions begun in mid-2016 on the maritime territorial issue were concluded by the end of the year.
One of the three officials, all of whom spoke on condition of anonymity, told Reuters the deal could be signed on Wednesday.
Cuba and the United States last week sealed an agreement to jointly prevent, contain and clean up oil and other toxic spills in the Gulf of Mexico, as the two sides seek to conclude deals that will make it harder for Trump to reverse a thaw in relations begun two years ago.
Trump has threatened to put an end to the fragile detente unless Havana makes more concessions.
International law gives countries the right to any resources found in the sea within 200 miles of their territory. But when the areas overlap, as they do in the case of the Eastern Gap, countries first must reach an agreement to develop them.
Mexico already has a cross-border agreement with the United States on developing potential oil and gas resources in the Gulf of Mexico, but not with Cuba.