“They will be taken to a safe facility by the intelligence officers who will go through a period of debriefing them and preparing them for a new life and arranging for new identities,” Fran Townsend told CNN television.

Townsend, the homeland security advisor to former president George W Bush, was speaking after the White House confirmed the CIA chief Leon Panetta had led negotiations with Russia for the biggest spy swap since the Cold War.

Ten convicted Russian agents were exchanged for four Russians convicted of spying for Western countries in a dramatic deal completed on Friday at Vienna airport.

But it was not immediately clear how many of the four released by Moscow arrived in the US, after their plane stopped briefly in England. Townsend said the CIA will offer the freed agents housing and financial assistance as they start their new lives. And they will quiz them closely to “understand what were the sorts of questions that Russian officials were asking them when they were in prison and arrested and how were they treated,” she said.

The debriefings, which could take weeks or even months, will help “from a counterintelligence perspective,” she added, saying: “We will likely learn a fair amount from these people.”

Children repatriated

Meanwhile, US attorney general Eric Holder on Sunday said that all the children of the 10 Russian spies freed in a dramatic swap with Moscow have been sent to Russia to rejoin their parents.

“The children have all been repatriated. We did so consistent with what their parents’ wishes were,” Holder said.

Holder did not give any figures for how many children were involved, but press reports said the 10 agents, some who were married to each other, could have had as many as seven children between them.