Instead, an unlikely outsider played a key role in closing out a final chapter of the Cold War.
Assuming a rare part in international diplomacy, Pope Francis stepped in to preserve the complex negotiations at crucial moments, then oversaw the final talks in Rome two months ago.
"Today we are all happy because we have seen how two peoples, who were far apart for many years, yesterday took a step to get closer," Francis, the first Latin American pontiff, declared Thursday at the Vatican.
President Obama had called for normalizing relations after he took office in 2009. But ending Cuba's isolation has been a goal far longer for the Argentine-born pope, who views the decades-old U.S. economic embargo as a source of division in the hemisphere and a cause of suffering for the Cuban people.
The pope worked behind the scenes after Obama sought his help March 27 during a visit to the Vatican. They talked for 45 minutes, with one translator each, at Francis' desk in the vast papal library, deep inside the Apostolic Palace.
It was their first discussion, and Cuba "got as much attention as anything else," said a senior Obama administration official who spoke on condition of anonymity to brief reporters.
Early in the summer, the pope wrote letters to Obama and Cuban President Raul Castro urging them to "resolve humanitarian questions of common interest," the Vatican said, particularly the release of Alan Gross, an American jailed in Cuba, and three Cubans imprisoned in Florida.
"We haven't received communications like this from the pope that I'm aware of other than this instance," the senior official said.
The pope's secret role in the back-channel talks was crucial because, as a religious leader with the confidence of both sides, he was able to convince the Obama and Castro administrations that the other side would live up to the deal, analysts said.
Austen Ivereigh, a British biographer of Francis, called the pope's mediation "the clincher" that brought the two adversaries together.
"It reflected the determination to work on the issue Francis had shown when he became pope in 2013," he said. "Francis is a genius at breaking through and building bridges across boundaries."
Obama chose two aides to lead the U.S. side — Benjamin J. Rhodes, a deputy national security advisor and speechwriter, and Ricardo Zuniga, a former U.S. diplomat in Havana who is senior director for Western Hemisphere affairs at the National Security Council.
They held their first face-to-face discussion with a Cuban team in Canada in June 2013. Over the next 18 months, they met half a dozen more times in Ottawa or Toronto. Canada did not participate in the talks.
Between meetings, they communicated through the American Interests Section in Havana, which is under Swiss protection, and the Cuban equivalent in Washington. They also sent messages via diplomatic missions at the United Nations in New York and in phone calls between U.S. Secretary of State John F. Kerry and Cuban Foreign Minister Bruno Rodriguez Parrilla.
The U.S. side was determined to win the release of Gross, 65, a U.S. government subcontractor who was arrested in 2009 by Cuban authorities for distributing communications gear to the island's small Jewish community. Cuba considered the activity a threat to the government.
Cuba wanted to trade Gross for three Cuban spies held in a federal prison in Florida. The three, remaining members of the so-called Cuban Five, are heroes in Cuba for spying on anti-Castro groups in Florida.
But the talks got hung up because the White House was unwilling to swap convicted spies for Gross. He was not an intelligence officer, they argued, but an illegally imprisoned U.S. citizen.
The problem was overcome when the U.S. side came up with a surprise solution. They suggested swapping the three spies for a former Cuban intelligence officer who was imprisoned in Cuba in 1995 after alerting U.S. authorities to a series
of Cuban spy rings in the United States. Castro's government agreed.
It was urgent that the talks remain secret, because a glare of publicity could allow opponents of normalization, including Florida's congressional delegation, to sound the alarm and derail them, officials said.
The negotiations became a race against time for another reason.
Gross was living in a grim 8-by-10-foot cell with two other prisoners. With only beds and a latrine, they lived under lights that blazed all night long. As time passed, Gross lost 100 pounds, and his health, including his eyesight, deteriorated.
His family worried that Gross' mental state was also deteriorating, especially when they learned he had begun unannounced hunger strikes out of despair. His wife, Judy, called on Obama to become personally involved.
Early this year, a group of U.S. lawmakers, including Sen. Patrick J. Leahy (D-Vt.) and Rep. Chris Van Hollen (D-Md.), met with Obama to convey their view that more needed to be done.
Also pushing for action was Kerry, who met Gross' family repeatedly and warned Cuba that Gross could die, embarrassing them and ruining chances for rapprochement. Kerry also reached out to Vatican aides for help.
Cuban officials seemed to have a variety of goals in the talks. They demanded an end to American programs promoting democracy, which they view as a security threat; closure of the U.S. naval station at Guantanamo Bay, in eastern Cuba; and an end to their nation's designation by the U.S. as a "state sponsor of terrorism."
But in time, it became clear that release of the three spies was a top priority, and one that the White House could deliver. As a deal took shape, Gross' family and supporters grew hopeful that he would soon be released.
But as summer turned to fall, they worried that the White House was preoccupied with other challenges, including efforts to seal an immigration deal in Congress, which might be threatened by a diplomatic breakthrough with Cuba.
Finally, in October, the negotiators met at the Vatican for a final session. Key players included Cardinal Pietro Parolin, the Vatican's secretary of state, and Cardinal Jaime Ortega, the archbishop of Havana, who is close to Francis.
The pope and his aides again urged the Cubans to go along with the prisoner swap. They also reviewed the steps both sides would take to normalize relations and expand business, travel and other opportunities.
The closing of the deal came off smoothly. Obama and Castro spoke by telephone Tuesday for nearly an hour, the first extended conversation between leaders of the two nations since the 1959 revolution that eventually brought communists to power.
And early Wednesday, a blue-and-white plane from Obama's presidential fleet flew to Havana, carrying a delegation of U.S. lawmakers, including Van Hollen, to bring Gross home.
Determined not to have Gross appear publicly in his prison garb, his lawyer, Scott D. Gilbert, bought khaki trousers and Oxford cloth shirts.
Gilbert had to buy a variety of sizes because, after Gross' five years in jail, "we didn't know what size he'd be any more," said Jill Zuckman, a spokeswoman for the family.
When the American delegation reached a building near the runway where Gross was waiting, he burst into a smile and hugged everyone in the room, one by one.
"And what a smile: It said, 'I wasn't sure I'd see this day,'" said Van Hollen.