Images have emerged of Sgt Bergdahl release on Saturday
US Defence Secretary Chuck Hagel says the decision to strike a deal with the Taliban for the release of a US soldier was unanimous in the White House.
Hagel told the BBC the agreement was made because it was believed Sergeant Bowe Bergdahl's life was "in peril".
Barack Obama's administration had to act quickly and without first consulting Congress, he added.
The president has been accused of contravening a law that requires giving Congress 30 days' notice.
Sgt Bergdahl was released on Saturday after five years in Taliban captivity.
"It was our judgement based on the information that we had that his life, his health were in peril," Hagel told the BBC.
"Can you imagine if we would have waited or taken the chance of leaks over a 30 day period?
"I will tell you what I know and I made a judgement on this too - that would have seriously imperilled us ever getting him out."