Mottaki told a news conference in Islamabad that no other contentious issues would be discussed.
"The negotiation is limited to [the subject of] Iraq, [taking place] in Iraq," Mottaki said.
He said the talks will be at the level of ambassador.
The United States has so far made no announcement. Recent reports suggested that U.S. Ambassador to Iraq Ryan Crocker would represent Washington at any Iranian-U.S. meeting.
Iranian Supreme Leader Ayatollah Ali Khamenei, who is the highest political and religious authority in the Shi'a-dominated republic, said on May 16 that any such meeting would focus solely on the "responsibility of the occupiers" in Iraq.
The United States has accused Iran of fomenting violence in Iraq by backing Shi'ite militia there, and of providing weapons and technology for new versions of roadside bombs used against U.S. troops.
Iran denies the charges and accuses the U.S. of igniting tension between Iraq's Shi'ite and Sunni Muslims.
Washington and Tehran also continue to disagree over Iran's nuclear activities. U.S. officials have also accused Iran of a covert effort to develop or possess nuclear weapons, a charge that Tehran has repeatedly denied.
The UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), has criticized Tehran for a lack of disclosure and said it cannot rule out weapons links to Iran's nuclear activities.
A recent "New York Times" report suggested that the IAEA will conclude in an upcoming report that Iran has made surprising advances in its nuclear efforts.