FACTBOX: Presidential candidates on Cuba's Castro

(Reuters) - Following are some previous comments by presidential candidates about Cuba, whose long-time but ailing ruler, Fidel Castro, said on Tuesday he would not return as president:

DEMOCRAT HILLARY CLINTON

The New York senator and former first lady has said significant change in Cuba is necessary before U.S. relations can be normalized.

"I think that has to be a precondition," Clinton said during a December debate. She said the Cuban people had "a tremendous pent-up desire" for fundamental democratic reforms.

REPUBLICAN JOHN MCCAIN

A former prisoner of war in Vietnam who is popular among conservative Cuban-Americans, has vowed not to lift the U.S. trade embargo against Havana until it holds free elections. He also has said he would keep up decades-old U.S. pressure for political change in Cuba's one-party state. That has included a travel ban and trade and financial sanctions enforced a few years after Castro's 1959 revolution on the Caribbean island.

The Arizona senator has also said Cubans participated in the torture of some of his fellow prisoners in Hanoi during the Vietnam War.

DEMOCRAT BARACK OBAMA

The Illinois senator has said he would be open to talking with U.S. adversaries including Castro. He also has said he would favor immediately loosening some aspects of the embargo, including restrictions on visits to Cuba and remittances to families.

(Compiling by Donna Smith in Washington; editing by Mohammad Zargham)