The decision that would launch one of the most intense and improbable negotiations in the history of U.S.-China relations was made in the space of hours — and it was sparked by a series of phone calls to the American Embassy.

Chen Guangcheng, the blind Chinese dissident, was somewhere in the sprawling edges of Beijing on Wednesday, April 25. His foot was broken in several places from a daring getaway from house arrest three days earlier, and his leg was beginning to swell. According to the activists who placed the initial calls, he was moving from place to place to avoid detection.

He was pleading for shelter.

The request hit the embassy like a rocket, setting off a flurry of secure calls among officials in Beijing and senior State Department officials in Washington. They weighed various scenarios, the possible diplomatic fallout with the Chinese, and the consequences for high-level meetings planned for the following week between Secretary of State Hillary Rodham Clinton and China’s top leaders.

The name Fang Lizhi quickly came up. The last Chinese dissident U.S. officials were known to have ushered into the embassy, in 1989, Fang had remained stuck behind its walls for more than a year, exacerbating friction between the United States and China.

With Chen, the embassy had been told there was a narrow window of opportunity because of his need to keep moving. Senior White House officials were briefed. Then Clinton relayed her ultimate decision to the embassy: Bring him in.

Talks with the Chinese began four days later.

“When we proceeded, we did it with clear eyes about what we were getting into,” said a senior administration official involved in the process, which culminated Saturday with Chen’s arrival in the United States.

For weeks, U.S. officials have kept secret many of the sensitive details about their negotiations over Chen’s fate. But with the 40-year-old lawyer safely aboard a plane Saturday, senior administration officials described extensively for the first time their dealings with the Chinese — how they struck the first deal only to have it fall apart, and how the negotiations almost collapsed again.

The officials, all of whom spoke on the condition of anonymity, detailed their efforts in the midst of continuing criticism by Republicans and some human rights groups over their handling of the crisis. Those critics argue that U.S. officials were too trusting of the Chinese and failed to secure hard guarantees — assertions Obama administration officials refute.

Diplomacy with China is often complicated by its government’s opaque nature, layers of bureaucracy, rule by the Communist Party and sometimes puzzling decision-making process.

But those involved in the negotiations said the high-stakes talks over Chen offer a rare glimpse into how China’s leadership operates in real time — under considerable internal and external pressures.

The Chinese Embassy did not respond to requests for comment for this story.

Two unidentified men

The negotiation room at the Foreign Ministry compound in East Beijing was set up with two long tables, each with a microphone. Elaborate Chinese art hung on the walls.