In the case of Cuba, the entire American delegation consisted of two White House officials, one of whom, Benjamin J. Rhodes, is a 37-year-old speechwriter who has worked for Mr. Obama since his 2008 campaign and has become an influential voice in the administration. The Iran and China negotiations were also led by trusted Obama aides.

Using non-diplomats helps preserve the veil of secrecy, a senior official said, because such people are less likely to arouse suspicion among colleagues or the press. The three countries with which they were negotiating, the official said, were also able to keep a secret.

“Negotiations are like mushrooms: They grow in the dark,” said Martin S. Indyk, the director of foreign policy at the Brookings Institution. “That’s especially true of negotiations between longtime adversaries, where the domestic politics on both sides make it impossible to reach a deal if the negotiations are conducted in public.”

Mr. Indyk knows firsthand the hazards of conducting diplomacy in open view. As the administration’s special envoy for Israeli-Palestinian negotiations, he struggled to bring together distrustful parties under a white-hot media glare. While the details of the talks were kept under wraps, the very public nature of the process made it vulnerable to scrutiny from all sides.

The last time Washington had a vigorous debate over the need for secrecy in diplomacy was in 2010 when WikiLeaks released 250,000 confidential State Department cables, forcing the Obama administration to mend fences with foreign leaders and others who had been slighted in the reports that diplomats sent in from the field. The damage from the WikiLeaks disclosures proved less severe or long-lasting than many people in the government predicted. But it did nothing to dissuade the Obama administration that fledgling initiatives needed to be shielded from the public and the press.