The US State Department says more detail is needed on Canberra's agreement with Iran to share intelligence on Australian foreign fighters.
The United States is seeking more information about the Abbott government's deal to share intelligence with Iran on Australians fighting with Islamic State.
A spokeswoman for the US State Department says more detail is needed on the unprecedented agreement, announced on Monday when Foreign Minister Julie Bishop was in the Iranian capital Tehran.
The US has ruled out co-ordinating with Iran on any response to the Islamic State threat.
"We've seen the reports and are trying to get a little more information about what that actually might look like," acting State Department spokeswoman Marie Harf said in Washington, when asked about Australia's deal.
"We just don't have a lot more details at this point," The Australian newspaper reports her as saying.
Independent MP Andrew Wilkie has criticised the "informal" intelligence-sharing deal, warning the regime in Tehran can't be trusted.
The former intelligence analyst described the deal as "utter madness from a security point of view".