The US-based West Papua Advocacy Team says that American security personnel on the ground at the Freeport mine in Papua are probably not active soldiers.
Members of Indonesia's House of Representatives have voiced concern about reports that there are up to 70 US servicemen deployed at Freeport's troubled gold and copper mine.
The Indonesian government has denied the reports, saying the Americans in question are security consultants working at Freeport.
The Advocacy Team's Ed McWilliams says the US government's response has been less than specific, but that it's not unusual for ex-soldiers to take jobs at Freeport.
"What we had seen was ex-military personnel who were taking jobs at Freeport, obviously offering security advice and so on but also, I think, providing a communications link between the US Embassy Defence Attache office and the situation in Freeport."