Manouchehr Mottaki said the negotiations would be exclusively about Iraq and that the first meeting, in the presence of Iraqi officials, would try to set a more detailed agenda.
"Nothing but Iraq is in the agenda of the talks between Tehran and the United States," Mottaki told reporters in Islamabad, where he has been attending a meeting of the Organization of the Islamic Conference.
In Baghdad, U.S. Ambassador Ryan Crocker appeared unaware of Mottaki's announcement, saying only that he hoped the talks would take place by the end of the month.
"I'm ready to sit down anytime they like," said Crocker, who is to lead the U.S. delegation.
Crocker said the U.S. will be pushing Iran to be a helpful neighbor, singling out allegations that Tehran is providing militants in Iraq with powerful roadside bombs that have been used to deadly effect against American troops.
He declined to be more specific about items that might be on the agenda, but said the talks would be an opportunity for Iran to move into a "whole new era in its relationship with Iraq."
Mottaki also gave no details of what Iran wanted to discuss. But he reiterated Tehran's objection to the continued presence of U.S. soldiers in its western neighbor.
"We do believe that a correct approach to Iraq should look to both points, or both areas of the difficulty. Terrorists say that 'We are doing this because of the foreign forces,' and the foreign forces [are] saying that 'We are here because of the terrorist groups,"' he said.
The agreement to hold the talks is seen as a political turnabout, but tensions between Washington and Tehran have been escalating.
The U.S. accuses Iran of arming and financing militants in Iraq — a claim Iran denies — and the two sides are also at loggerheads over Tehran's nuclear program.
U.S. Vice President Dick Cheney warned Iran last week during a visit to the Gulf that the U.S. and its allies would prevent the country from developing nuclear weapons and dominating the region.
Iran denies seeking to build nuclear weapons and accuses the U.S. of seeking to topple its government.
Mottaki said Iran's top nuclear negotiator, Ali Larijani, and European Union foreign policy chief Javier Solana would resume their talks seeking to break the deadlock next week in Spain or another European country.
He said Iran was "flexible" and was seeking to remove "ambiguities" about its intentions. But he gave no indication that Iran would agree to the U.N. demand that it freeze uranium enrichment, a process that can produce material for nuclear bombs as well as civilian power stations.
He accused some countries, without naming any, of exerting unfair pressure on members of the U.N. Security Council, which has already introduced limited sanctions against Iran over the nuclear issue.
In an apparent reference to Washington's refusal to rule out the use of force against Iran, Mottaki said that military might alone was no longer enough to guarantee of success in foreign policy.
He said both the U.S. invasion of Iraq and Israel's war in Lebanon last year, which pitted it against Hezbollah fighters backed by Iran and Syria, failed in the face of "resistance," Mottaki said.
"We do believe that ... resistance now is [an] essential part of the belief of the Islamic ummah [community], of the Middle East people."