U.S.-Cuba relations: key dates in their diplomatic history

Fidel Castro, centre, speaks with Soviet Premier Nikita Khrushchev, right, as his Foreign Minister Raul Roa looks on, Sept. 20, 1960. (AP / Prensa Latina via AP Images)

Key events in U.S.-Cuba relations:

Jan. 1, 1959: Fidel Castro's rebels take power as dictator Fulgencio Batista flees Cuba. The United States soon recognizes the new government.

June 1960: Relations begin to sour as Castro veers left. Cuba nationalizes U.S.-owned oil refineries after they refuse to process Soviet oil. Nearly all other U.S. businesses are expropriated by October.

October 1960: Start of U.S. embargo: Washington bans exports to Cuba, other than food and medicine.

Jan. 3, 1961: U.S. breaks relations with Cuba and closes embassy.

April 16, 1961: Castro declares Cuba a socialist state.

April 17, 1961: U.S.-trained Cuban exiles stage the failed Bay of Pigs invasion aimed at toppling Castro. U.S. intelligence agencies also stage repeated attempts over the years to kill the Cuban leader.

Feb, 7, 1962: President John F. Kennedy expands embargo, banning almost all Cuban imports.

October 1962: U.S. blockade forces removal of Soviet nuclear missiles from Cuba. U.S. President John F. Kennedy agrees privately not to invade Cuba.

April 1980: Mariel boatlift: Cuba says anyone can leave; some 125,000 Cubans flee, causing a refugee crisis for the United States.

December 1991: Collapse of Soviet Union devastates Cuban economy.

August 1994: Castro declares he will not stop Cubans trying to leave; some 40,000 take to sea heading for United States.

Sept. 12, 1998: Five Cuban spies arrested in the United States. They are later convicted. Cuba mounts an international campaign to free them, saying they were defending island against U.S.-based terror attempts.

July 31, 2006: Fidel Castro announces has had operation, temporarily cedes power to brother Raul. Fidel resigns as president two years.

Dec. 3, 2009: USAID contractor Alan Gross arrested in Havana, stifling incipient efforts to improve U.S.-Cuba ties under President Barack Obama.

Dec. 17, 2014: Gross freed and remaining members of Cuban Five spy ring freed as part of prisoner exchange.