The United States and Cuba have signed a treaty on maritime boundaries in the eastern part of the Gulf of Mexico.
A State Department statement said the pact covers the only water boundary not under a previous deal between the two countries.
The treaty will have to be approved by the U.S. Senate before it can take effect.
Cuba also signed a similar treaty with Mexico to sort out claims in the same part of the Gulf of Mexico.
The three countries had discussed the boundaries since the middle of last year.
The U.S.-Cuba treaty comes days before Republican Donald Trump becomes president. He has threatened to reverse moves by President Barack Obama to thaw relations between the countries, which included reestablishing diplomatic relations and easing a travel ban.