The Ostend Manifesto was a document written in 1854 that described the rationale for the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 to purchase Cuba

Cuba

The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...

 from Spain

Spain

Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

 and implied the U.S. should declare war if Spain refused. Cuba's annexation had long been a goal of U.S. expansionists, particularly as the U.S. set its sights southward following the admission of California

History of California

The history of California can be divided into several periods: the Native American period; European exploration period from 1542 to 1769; the Spanish colonial period, 1769 to 1821; the Mexican period, 1821 to 1848; and United States statehood, which continues to the present day...

 to the Union. However, diplomatically, the country had been content to see the island remain in Spanish hands so long as it did not pass to a stronger power such as Britain or France.