His comments followed a call by French Foreign Minister Laurent Fabius on Wednesday for all countries in the region, including Iran, to join the fight against Islamic State (IS) fighters who have seized swathes of Iraq as well as neighbouring Syria.
“If we agree to do something in Iraq, the other side of the negotiations should do something in return,” the official IRNA news agency quoted Zarif as saying.
“All the sanctions that are related to Iran’s nuclear programme should be lifted,” he said.
It is the first time that Iran has explicitly linked its readiness to work with the West in Iraq with a lifting of the crippling EU and US sanctions imposed over its nuclear programme.
Those sanctions are the subject of ongoing talks between Tehran and the major powers that are due to resume before the opening of the UN General Assembly next month.
In return for lifting the sanctions, the Western powers are demanding that Iran sharply rein in its nuclear programme to ally international concerns about its ambitions as part of a comprehensive deal they are seeking to strike by November.
The Iranian foreign ministry confirmed on Wednesday that discussions were under way with several European governments about the possibility of joint action against IS in Iraq.
Zarif said tough negotiations were still under way over what role Iran might play in Iraq and what the reward might be for its cooperation.
“It is still not clear what we have to do in Iraq and what they have to do in return,” the Mehr news agency quoted the Iranian foreign minister as saying.
“And that’s exactly the difficult part.”
Iranian and US officials discussed the jihadists’ lightning offensive in Iraq in June on the sidelines of nuclear talks with the major powers but both sides ruled out joint military action at the time.
Tehran and Washington have had no diplomatic relations since the aftermath of the Islamic Revolution of 1979, although they have had contacts over Afghanistan as well as Iraq.