Fidel Castro celebrated his 89th birthday in true form on Thursday, claiming that Cuba is owed "many millions of dollars" by the U.S. as a result of the half-century-old American trade embargo.

The U.S. put communist Cuba under a trade embargo in 1962, three years after Castro seized power by ousting a U.S.-backed regime. The decision remains in effect despite efforts by President Barack Obama, who wants Congress to lift it, Manila Bulletin reported.

U.S. officials say revoking the embargo will take time and it cannot be seen as an automatic part of the restoration of ties. Many Republicans oppose Obama, insisting that Cuba improve its human rights record before the embargo can be lifted, according to The Daily Star.

"Cuba is owed compensation equivalent to damages, which total many millions of dollars, as our country has stated with irrefutable arguments and data in all of its speeches at the United Nations," Castro wrote in an essay published in local media without going into detail on precisely how much money he reckons Washington owes Havana, AFP reported.

The essay comes not only on Castro's birthday, but also a day before U.S. Secretary of State John Kerry is scheduled to visit Cuba to reopen the U.S. embassy as part of the restoration of diplomatic relations between the U.S. and Cuba.

Castro has been a frequent contributor of essays to the communist party newspaper Granma and other media over the years, according to AsiaOne. "Writing is a way to be useful, if you keep in mind that we poor humans must be more and better educated in the face of the incredible ignorance that surrounds us all, except for researchers who use science to seek a satisfactory answer," Castro wrote.