"An agreement was reached to hold these negotiations, but their date will be determined later," Hassan Kazemi Qomi said.
He denied statements from some Iraqi officials that the previous date (March 6) had not been approved by the Iraqi authorities.
The talks were originally scheduled for mid-February, but were postponed for technical reasons.
The U.S. and Iran held their first three rounds of talks in Baghdad last summer, pledging to set up a three-party committee on Iraq's security and defense capabilities. They were the first direct talks between the two countries since they severed relations in 1979 following the Islamic Revolution which overthrew the U.S.-backed Shah.
Washington has previously accused Iran of providing training and weapons to militants in Iraq, plagued by violence since the formal end of the U.S.-led invasion of the Middle East state in 2003. Tehran denies the accusations.
