US President Barack Obama has said he "absolutely makes no apologies" for the deal to swap five Guantanamo Bay detainees for the Taliban-held American soldier Sgt Bowe Bergdahl.
"As commander-in-chief I am responsible for those kids," Mr Obama said.
The government has faced criticism for the deal amid claims by some US soldiers that Sgt Bergdahl deserted.
Sgt Bergdahl is recovering at a base in Germany, officials say, but he has not yet called his family.
Sgt Bergdahl was freed after five years in captivity in exchange for the five Taliban prisoners. They have been transferred to the custody of the Gulf state of Qatar, which brokered the deal.
Mr Obama was speaking in Brussels, where he has been attending a G7 summit.
He said: "We saw an opportunity and we seized it. And I make no apologies for that," adding that Sgt Bergdahl's deteriorating health was a "deep concern".
Mr Obama said: "Because of the nature of the folks that we were dealing with and the fragile nature of these negotiations, we felt it was important go ahead and do what we did."
He also defended making a White House press call alongside Bowe Bergdahl's parents, saying it was "not a political football".
"You have a couple of parents whose kid volunteered to fight in a distant land, who they hadn't seen in five years and weren't sure whether they'd ever see again."
The White House is required to notify Congress 30 days before transferring detainees from Guantanamo Bay but decided that waiting was too risky.
Mr Obama argued that his administration had discussed the possibility of such an exchange with Congress in the past.
He also said the furore in Washington over the deal was "par for the course" and that he was "never surprised by controversies that are whipped up" there.
Earlier, Defence Secretary Chuck Hagel told the BBC the decision to strike a deal with the Taliban was unanimous in the White House.
Associated Press also quoted US officials as saying that Congress was not told of the swap because the Taliban had threatened to kill Sgt Bergdahl if details were leaked.
Meanwhile, a Pentagon spokesman said Sgt Bergdahl's health was improving daily at the Landstuhl centre in Germany and he was becoming more involved in a "decompression" plan to aid his return to the US.
Col Steve Warren said there was no date set for the first phone call to the family in Idaho, or for his transfer home.
A celebration rally in Sgt Bergdahl's home town of Hailey, Idaho, scheduled for later this month, has been cancelled.
Organisers said the event was called off for safety reasons after a large increase in the number of expected attendees.
Authorities in Hailey, a small town of 8,000 people, said they had been inundated with messages of protest and complaint about the event.
The circumstances of Sgt Bergdahl's capture in 2009 remain unclear, although the Pentagon has concluded he left his post in Paktika province without authorisation.