Maurizio Scelli, the outgoing head of the Italian Red Cross, said the deal had been kept secret from the US.

"Had the Americans known about it, this could have damaged the subtle strategy," Mr Scelli told Italy's Rai radio after speaking to a newspaper.

Two aid workers, Simona Pari and Simona Torretta, were held for three weeks.

Mr Scelli - who first revealed the story to the Italian daily La Stampa - said Prime Minister Silvio Berlusconi's right-man man, Gianni Letta, was aware of the deal.

"He acknowledged it and - albeit with a thousand recommendations - he told me to go ahead with it," Mr Scelli said.

Mr Berlusconi's office has not commented on the report. Italy has always denied paying a ransom for "the two Simonas".

Agent's advice

Mr Scelli said he did not know the identities of the insurgents his agency had treated.

"We collected them in the place we had been told and then took them to hospital with a series of precautions for them to be admitted into hospital as quickly as possible and without any hindrance," he told Rai.

He added that US checkpoints were among the hindrances he was referring to.

An Italian secret service agent, Nicola Calipari, was killed by US gunfire at a checkpoint in Iraq in March as he escorted another Italian hostage to freedom.

The US and Italy disagreed about the circumstances of the killing, briefly straining relations between the allies.

Mr Scelli said Mr Calipari had been consulted about the deal to free Ms Torretta and Ms Pari.

The two women stunned Italy by defending the Iraqi insurgency on their release, saying there was a difference between guerrillas and freedom fighters.