The Venezuelan government has formally donated an island near Philadelphia back to the United States.
Petty Island, an uninhabited island some 528 acres (214 ha) in size, is situated in the Delaware River in the state of New Jersey.
It was bought by Venezuela's state-run energy company, PDVS, in 1990.
Venezuelan President Hugo Chavez announced the move at a regional summit last week as part of an improvement in ties between the two nations.
At the Summit of the Americas in Trinidad and Tobago, President Chavez presented Barack Obama with a gift of a book: The Open Veins of Latin America by Eduardo Galeano.
The book is widely considered the bible of the Latin American left.
But the BBC's Will Grant, in Caracas, says Mr Chavez also gave Mr Obama something much bigger: Petty Island.
The Venezuelan government has used it for fuel storage and refinement since 1990.
Our correspondent says that in recent years the tiny island has been the subject of some controversy, with waterfront property developers pushing to construct a golf course, hotels and a casino on the site.
Environmental groups have opposed such measures, saying it has unique flora and fauna which must be conserved.
Now, as part of what the government has called a renewed spirit of co-operation between Venezuela and the US, Mr Chavez announced that the island would return to the US for environmental conservation projects.
While Mr Chavez's gift of a book to his US counterpart may have made headlines around the world and launched the publication up the New York Times bestseller list, the return of Petty Island may prove a more lasting donation our correspondent adds.