Speaking at the US ambassador's residence in Paris after an international meeting on security and peace in Iraq, Kerry said: " We are not coordinating with Iran."
"I have no idea of what interpretation they drew from any discussion that may or may not have taken place," Xinhua quoted Kerry as saying.
Kerry's remarks came after Iran's supreme leader, Ayatollah Ali Khamene, said Iran rejected a US invitation to coordinated fight to eradicate Islamist insurgents that have seized major cities in northern Iraq and Syria and threatened to establish an Islamic State in the region.
Kerry: We are not coordinating with Iran
Tehran was absent at Paris conference where participants agreed to offer the needed military support to Iraqi authorities to face "a global threat" of terrorism.
The move came ahead of top diplomats from the US, Britain, France, Germany China and Russia's meeting with the Iranian negotiators Thursday to reach lasting accord on their nuclear programme.
Kerry said he hoped "to find a way to reach an agreement that is important to the world but there is some very difficult issues."
In exchange for limited sanctions relief, Iran accepted last November to halt enrichment above five percent and neutralising its stockpile of near 20 percent uranium by means of dilution or converting and to not installing more centrifuges.
However, Western powers asked Tehran to close more centrifuges to not build a nuclear power.