Prize trustees said that starting in 2014, the prize will be open to all novels written in English and published in Britain, regardless of the author's nationality.
Founded in 1969, the Booker has previously been open only to writers from Britain, Ireland and the 54-nation Commonwealth of former British colonies.
That has not kept the award officially known as the Man Booker Prize after its sponsor, financial services firm Man Group PLC from becoming one of the world's best-known literary prizes, one that carries both prestige and commercial clout. Past winners include V.S. Naipaul, Salman Rushdie, Margaret Atwood, Ian McEwan and Hilary Mantel.
"We are embracing the freedom of English in all its vigor, its vitality, its versatility and its glory wherever it may be. We are abandoning the constraints of geography and national boundaries."
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Organisers said the decision had been made to resolve the paradox of "the most important literary award in the English-speaking world" not being open to all English-language writers.
They said they had considered setting up a separate US prize, but rejected the idea for fear of "jeopardizing or diluting" the existing award.
Among the six finalists for the 50,000 pound (USD 78,000) prize this year are several writers with strong US ties, including Jhumpa Lahiri and Ruth Ozeki. The winner will be announced at a ceremony in London on Oct. 15.