Ostend Manifesto, title of a document drawn up at Ostend (Oostende), Belgium, on October 9, 1854, by James Buchanan, the U.S. minister to Britain, later the 15th U.S. president; John Young Mason, U.S. minister to France; and Pierre Soulé, U.S. minister to Spain. Soulé had previously entered into negotiations with the Spanish government for the purchase of Cuba by the United States. His diplomatic blunders incurred the censure of his superiors, who ordered him to consult with the other two envoys. The result of this conference was the Ostend Manifesto, which urged Spain to sell Cuba to the U.S. and implied that the U.S. would use force if Spain refused. Publication of the manifesto caused a sensation among antislavery forces in the U.S., who feared that the acquisition of Cuba, where slavery was a well-established institution, would strengthen the proslavery forces. The controversy soon abated, however, and new grounds for conflict between the North and South were avoided, when the U.S. government repudiated the manifesto.