"We haven't reached the 90th minute yet," the president of the football-mad Islamic republic said when asked if Iran would wait until the last minute before bowing to an International Atomic Energy Agency (IAEA) deadline.
"And frequently there is five to six minutes of extra time," added Khatami as he left a cabinet meeting.
The IAEA's board of governors on September 12 gave Iran until the end of this month to guarantee it is not developing and will not develop nuclear weapons.
The IAEA has asked Iran to produce a detailed list of its nuclear-related equipment, cease uranium enrichment and sign an additional protocol to the nuclear Non-Proliferation Treaty (NPT) allowing tougher inspections.
Iran has said it is not bound by the resolution -- passed after heavy US lobbying -- but will nevertheless try to answer the IAEA's concerns.
A failure by Iran to meet the IAEA deadline could see it being declared in violation of the NPT and the matter being passed to the UN Security Council, which could impose sanctions.