Iran denied a report that it is ready to help counter Islamic State insurgents in return for progress in negotiations with world powers over its nuclear programme.
France, one of the six nations in nuclear talks with Tehran, said on Wednesday it wanted Arab states, Iran and the five permanent members of the UN Security Council to coordinate a comprehensive response against Islamic State, whose militant forces control large parts of Syria and Iraq.
The Sunni Islamist insurgency threatening to tear apart Iraq has alarmed both Shi'ite Muslim Iran and the United States, which have had no diplomatic relations since soon after the 1979 Islamic Revolution in Tehran.
On Thursday a story from the official Iranian News Agency (IRNA) cited by several news organisations including Reuters reported Foreign Minister Javad Zarif as saying that if Iran agreed to "do something in Iraq, the other side in the negotiations will need to do something in return".
"All the sanctions imposed on Iran over its nuclear activities should be lifted in return for its help in Iraq," it quoted him as saying.
But later on Thursday IRNA reported foreign ministry spokeswoman Marzieh Afkham as dismissing "reports by some news agencies about Iran and US cooperation in Iraq".
"These reports are a misinterpretation of the foreign minister's remarks and are 'totally baseless'," IRNA reported her as saying.
IRNA did not elaborate. On Friday, the story on IRNA's website still showed remarks attributed to Zarif but the word Iraq had been omitted. A similar report by the semi-official Mehr news agency about Zarif's comments continued to cite him mentioning Iraq.
Iran has offered to cooperate with the United States on stabilising Iraq, which like Iran has a majority Shi'ite population, but Washington has responded cautiously.
Western officials have repeatedly said they do not want to mix the nuclear dossier with events elsewhere in the region.
In Washington, State Department deputy spokeswoman Marie Harf said she understood that Zarif's comments did not refer to Iraq and instead referred to Arak, the site of a facility that is one of the topics under discussion in nuclear negotiations between Tehran and six world powers.
Iranian officials could not immediately be reached for comment on whether Zarif had mentioned Arak or not.
Harf told reporters: "We understand that the Iranian foreign minister - and you're never going to believe this - quoted in the story as referring to Iraq the country was actually referring to Arak, the Iranian nuclear facility. We've looked at the language a couple of times, actually, and think he was not linking in that specific quote fighting ISIS in Iraq to lifting of Western sanctions. He was talking about making progress on Arak, the nuclear facility, to lifting of Western sanctions."
French Foreign Minister Laurent Fabius urged Iran on Wednesday to be part of any coordinated action against Islamic State but said that the Iraq and nuclear issues should be dealt with independently.
"We shouldn't exchange one thing for another. While it seems indispensable that Iran participates (in an Iraq conference), it's not because it participates that we are going to say the Iran nuclear problem is resolved," said Fabius, whose country has traditionally maintained a tough stance in the Iran talks.
"These are two problems of a different nature and it would be dangerous to enter into a system where each side exchanges something for another. So let's be careful about that."
The United States and some of its allies suspect Iran is using its civilian nuclear programme as a cover to develop atomic bombs. Iran denies this, saying that it is enriching uranium solely for civilian energy purposes.
Six global powers and Iran failed to meet a July 20 deadline to negotiate a comprehensive agreement under which Iran would curb its nuclear activities in exchange for the easing of economic sanctions that have crippled its economy.
The six - Britain, China, France, Germany, Russia and the United States - have agreed to extend the deadline to reach a long-term, overall agreement until November 24.
They are set to hold a new round of talks with Iran ahead of next month's UN General Assembly in New York.