"In the next few days we will sign it," Kamal Kharazi told reporters when asked to say when Iran would sign the additional protocol to the nuclear Non-Proliferation Treaty (NPT).
Kharazi, speaking during a press conference with visiting Indian Foreign Minister Yashwant Sinha, said the signing had been given final approval by both the cabinet and the Supreme National Security Council, Iran's top decision-making body on security issues.
Iran has been under international pressure to sign the text in Vienna, amid suspicions the Islamic republic is using a civil atomic energy programme as a cover for secret nuclear weapons development.
Last month, the IAEA condemned Iran for 18 years of covert nuclear activities although a report said there was no clear evidence the country has been developing nuclear arms.
IAEA director Mohamed ElBaradei argues that the agency needs more powers as it continues to probe Iran, including the ability to carry out surprise inspections of suspect nuclear sites. Under the original NPT, the IAEA is only authorised to carry out pre-arranged site inspections.
Iran had been resisting the additional protocol, arguing that inspectors could violate national sovereignty and probe sites that are crucial to the defence of the country, lumped into an "axis of evil" by US President George W. Bush along with North Korea and the regime of former Iraqi dictator Saddam Hussein.
The country finally bowed to pressure after the IAEA threatened to refer its concerns to the United Nations Security Council, which would have left Iran open to possible sanctions.
That U-turn came in October during an unprecedented visit by the foreign ministers of the European Union's big three -- Britain, France and Germany. Iran agreed to sign the additional protocol, hand over full details of its activities and suspend uranium enrichment.
Although the deal has been given the blessing of supreme leader Ayatollah Ali Khamenei, who has the final say on all matters of state, a number of influential conservatives have voiced their fierce opposition to allowing the tougher inspections.
Several had gone so far as to advocate following the path of fellow "axis of evil" member North Korea and pull out of the NPT altogether.