By Andrew North
BBC correspondent in Kabul
The US Department of Defense has admitted having contact with a former US soldier, Jonathan Idema, charged in Afghanistan with torturing civilians.
Mr Idema says that all his evidence has been handed over to the FBI
But it says it rejected Mr Idema's offer to work together in capturing terror suspects in Afghanistan.
Mr Idema - who was arrested by Afghan security agents in July - says his operation was approved by the US.
He and two other US citizens are being tried for torture, kidnapping and running a private jail in Kabul.
When Jonathan Idema, also known as Jack, first appeared in court in Kabul last month, he was asked to prove his claims to have had links with the US Department of Defense.
One name he mentioned was Heather Anderson, the Pentagon's Acting Director of Security, who answers to the chief official responsible for intelligence matters in the office of Donald Rumsfeld, the US Defence Secretary.
Mr Idema said Ms Anderson had applauded their work in Afghanistan and had wanted them to go on contract.
Until now, the Department of Defense has refused to acknowledge any contacts at all between itself and the former US soldier, who it has described as an unauthorised freelancer.
But a Pentagon official has now told the BBC that Mr Idema spoke to Ms Anderson by phone earlier this year.
After doing some checking on Mr Idema, the official said, she then called him back.
But Ms Anderson had turned down what she said was Mr Idema's request to be taken on by the Pentagon to work in Afghanistan.
That was not the end of the matter.
The official said Mr Idema continued to contact the Pentagon by phone, fax and email, "trying to establish a relationship".
Jack Idema's US-based lawyer, John Tiffany, has rejected the Pentagon's version of events, describing them as completely false.
If they had rebuffed him, he asked, why did they keep taking his phone calls?
On the one hand, the Pentagon's admission could be seen as another concession to Mr Idema's story.
On the other hand, it proves nothing more than that some telephone conversations took place.
The US military has already admitted receiving a detainee from Mr Idema, although this man was later released.
Mr Idema and two other Americans deny the charges of torture and kidnapping.
If found guilty, they face up to 20 years in jail.
During the his trial, Mr Idema has alleged that hundreds of videos, photos and documents were removed by FBI officers after his arrest in Kabul.
He said the documents would prove that "while we were not in the United States army, we were working for the United States army".