Iran's official Islamic Republic News Agency (IRNA) quoted Mottaki as saying Iran would consider talks at the level of deputy foreign ministers if Washington makes an official request.
U.S. State Department spokesman Sean McCormack said Washington had no plans to open such talks, as it had already established a channel with U.S. Ambassador to Iraq Ryan Crocker.
Crocker and Tehran's envoy Hasan Kazemi-Qomi met in Baghdad on July 24 for a second round of talks about security in Iraq.
A first round of talks was held in May, the highest-level meeting between the two countries since 1980.
Crocker accused Iran of increasing its support for militants in Iraq.
But he announced that Iran, Iraq, and the United States had agreed to set up a special panel to explore ways to stabilize Iraq.
(Reuters, AP, AFP)