Alan Gross: Cuba Releases American After Five Years in Prison The move represents a first step toward normalizing U.S.-Cuba relations.

 -- American contractor Alan Gross has landed in the U.S. after being released earlier today from a Cuban prison where he had been held for five years.

In a landmark humanitarian prisoner exchange announced this afternoon by President Obama at the White House, the agreement was reached following more than a year of secret back channel talks at the highest levels of both governments.

Today’s release of Gross, 65, who is said to be in poor physical condition, represents a first step toward normalizing relations with the neighbor just 90-miles off the Florida coast.

The U.S. and Cuba are going to immediately begin talks to restore diplomatic relations, the White House announced.

“What we are doing is beginning the normalization of relations between the U.S. and Cuba,” a senior administration official said.

In the coming months, the U.S. also plans to re-establish an embassy in Havana, Obama said.

"Today, the United States is taking historic steps to chart a new course in our relations with Cuba and to further engage and empower the Cuban people," Obama said. "We are separated by 90 miles of water, but brought together through the relationships between the two million Cubans and Americans of Cuban descent that live in the United States, and the 11 million Cubans who share similar hopes for a more positive future for Cuba."

Today’s announcement comes after Obama and Cuban President Raul Castro spoke by phone Tuesday. Their conversation was described as a “summing up” of the work that has been done over the past year leading up to these changes. The two leaders discussed issues of importance in the hemisphere, while also noting that they will have differences to come. According to a senior administration official, Obama made clear his intent to maintain U.S. advocacy for human rights in Cuba.

Gross was convicted of espionage by a Cuban court in 2011 and sentenced to 15 years for bringing telecommunication devices into Cuba while working as a subcontractor for United States Agency for International Development.

The Cuban government accused him of being party to a U.S.-led plot to overthrow the government through an “Arab spring.”

Following a recent visit, Gross’ attorney described him as nearly toothless, barely able to walk because of arthritis in his hips and blind in one eye. He has been kept in a small room at a military hospital 24 hours a day with two other Cuban political prisoners.

Gross has refused medical and dental care or outside privileges, and declined visits and food from the U.S. Interest section in Havana. He had promised a hunger strike leading to death if not released by the end of this year.

In a statement released earlier this month to mark the anniversary of Gross’ time in jail, Gross’ wife Judy said: “Enough is enough. My husband has paid a terrible price for serving his country and community.”

In return for Gross, the United States has agreed to the humanitarian release of three Cuban agents convicted of espionage in a controversial trial that found them guilty of spying on anti-Castro groups in Miami, but not the U.S. government. All three were most recently held in North Carolina at a federal medical facility for the U.S. Bureau of Prisons.

The humanitarian release is just the beginning of a promised new relationship with Cuba. The White House is indicating the beginning of new talks on everything from travel restrictions to eventual lifting of the Cuban embargo in place since John F. Kennedy was president.

In an interview last week with Jorge Ramos for Fusion -- a sister network to ABC News -- President Obama said: “We’ve been in conversations about how we can get Alan Gross home for quite some time.”

"We continue to be concerned about him. We think that he shouldn’t have been held in the first place,” Obama told Ramos. “With respect to Cuba generally, I’ve made very clear that the policies that we have in making remittances easier for Cuban families, and making it easier for families to travel, have been helpful to people inside Cuba... But the Cuban government still needs to make significant changes."

ABC's Mary Bruce contributed to this report.

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