WASHINGTON » Of all the tense moments in the year and a half of secret negotiations to free Alan P. Gross from Cuba, none may have matched a meeting in Ottawa, Ontario, early last June between a two-person White House delegation and their Cuban counterparts.

Sgt. Bowe Bergdahl, the American soldier imprisoned for nearly five years in Afghanistan, had just been freed in return for five Taliban commanders held at Guantanamo Bay, Cuba. The Cuban negotiators seized on his release as a precedent that would allow a reluctant White House to agree to a swap of Gross for three Cuban agents jailed in the United States, according to a senior administration official.

The Cubans were panicked: At that moment, in Plano, Texas, Gross’ mother, Evelyn, was in the last stages of a battle with lung cancer. (She died on June 18.) The Cubans were fearful that her death would drive Gross to kill himself, depriving them of their most valuable chip to win the freedom of their agents, who had become folk heroes in Cuba.

For the White House, however, Bergdahl’s release was a new roadblock. Freeing the soldier, who had walked off his post, in exchange for Taliban fighters provoked such a barrage of criticism in Congress that White House officials told the Cubans that any deal would have to be more than a simple quid pro quo.

"We made the point: ‘This shows you how controversial swaps are. This is something we are only willing to consider in the context of an appropriate exchange,’" said a senior official, speaking on the condition of anonymity to discuss internal negotiations. "The important thing was not to see the swap as the end, but the gateway to the policy changes."

In the end, the deal for Gross also included the re-establishment of diplomatic ties between the United States and Cuba after 53 years of estrangement, an agreement to release 53 political prisoners and the freeing of a Cuban intelligence officer, Rolando Sarraff Trujillo, who had worked for the CIA.

But it also took another six months, and the personal intercession of Pope Francis, to nail down the details. People close to Gross attribute that delay largely to the shadow of Bergdahl. During that period, Gross’ emotional condition continued to deteriorate, and the White House became as worried as the Cubans about his survival.

"The Cubans thought the Bergdahl prisoner exchange made it easier," said Tim Rieser, a senior aide to Sen. Patrick J. Leahy, D-Vt., who conducted his own negotiations with Cuban officials for two years on behalf of Gross. "I told them it made it harder for the president and they needed to make it easier."

Rieser, who was not involved in the White House talks but was briefed regularly on them, said he tried to explain to the Cubans the political sensitivities of the Bergdahl case for President Barack Obama. Having witnessed the toxic reaction on Capitol Hill, Rieser said he made it clear to them that a deal for Gross could not look like a replay.

"I told them you’ve got to put yourself in Obama’s shoes," Rieser said. "It’s a politically difficult decision for him, and he’s got 50 other more important issues on his desk right now."

The two White House officials, Benjamin J. Rhodes and Ricardo Zzqiga, flew to Ottawa right after Obama returned from a trip to Europe that had been dogged by the Bergdahl case. Obama’s national security adviser, Susan E. Rice, came under fire after saying that Bergdahl had served with "honor and distinction," regardless of the questions about why he walked off his military outpost in a remote corner of Afghanistan.

There were distinct parallels between the two cases. For more than a year, until early 2012, the Obama administration had tried to negotiate Bergdahl’s release as part of a broader political settlement with the Taliban, in which they would renounce terrorism and take steps to reconcile with the Afghan government.

The White House abandoned those efforts when it became clear, after the United States announced its plan to withdraw combat troops, that the Taliban were no longer interested in a bigger deal. Amid fears that Bergdahl’s life was in jeopardy — another echo of the Gross case — the American focus narrowed to a straight swap.

But the negotiations for Gross played out in reverse order. Initially, the State Department demanded that the Cubans release him, refusing to consider any broader deal. Leahy told Obama that Gross would never be freed unless the United States was willing to negotiate over the three agents, who were part of a group originally known as the Cuban Five.

After Obama was re-elected, he made normalizing relations with Cuba a top priority — one that depended on freeing Gross. In choosing Rhodes and Zzqiga to open a direct channel, the president authorized them to expand the talks to include the Cuban agents, political prisoners and the goal of re-establishing diplomatic ties.

At the White House, only a tight circle of aides was told of the back channel. To preserve their secrecy, they code-named the negotiations Project Ardilla, using the Spanish word for squirrel, after Secret Squirrel, the swashbuckling, bucktoothed rodent in the vintage Hanna-Barbera cartoon.

Before settling on the package announced this month, the two sides talked about other potential exchanges, including swapping felons. Among those discussed was Joanne Chesimard, a former Black Panther who fled to Cuba after being convicted in 1977 of killing a New Jersey state trooper. But she has asylum in Cuba, and the Cubans had their own list of felons here whose release would be politically contentious.

As the summer wore on, officials said, the administration did what it could to try to improve Gross’ mental state. Secretary of State John Kerry sent him a handwritten letter after the death of his mother, imploring him not to lose hope. The White House negotiated with the Cubans to allow him more calls and access to email.

But the willingness of White House officials to risk waiting another six months attests to the political pressures they faced. After all, previous presidents, from John F. Kennedy to Jimmy Carter, approved straight spy swaps with Cuba, said Peter Kornbluh, an author of "Back Channel to Cuba," about the history of secret talks between the two countries.

"What is unprecedented is the U.S. argument that the swap had to have some equivalence," said Kornbluh, who is a senior analyst at the National Security Archive in Washington. "Negotiations in foreign policy don’t have to be equivalent. They just have to meet the needs to both sides."

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