Iran is preparing a criminal complaint to present at any international court that may try Saddam Hussein over the 1980-1988 Iran-Iraq war.Around 300,000 Iranians were killed in the war, including thousands in chemical weapons attacks by the Iraqi army.
"The Foreign Ministry has taken some measures on this issue and has collected the necessary documents. I hope we can defend Iranians' rightful demands at a proper place," government spokesman Mr Abdollah Ramazanzadeh told a news conference.
Mr Ramazanzadeh said that while the Iraqi people have priority in trying Saddam, "that doesn't negate the rights of others for filing a suit at international circles against him".
"We naturally want him to stand trial at a fair international court and such a court should look into the crimes of this dictator," he added.
"It should become clear at such an (international) court who were those who mobilised this dictator to create turmoil in the region," Mr Ramazanzadeh said.
Iran has long held that the US and western European countries armed Saddam against Iran which, after the 1979 Islamic revolution, was perceived as a bigger regional threat by the West.
The official IRNA news agency reported that Iran's judiciary had written to the UN Secretary-General, Mr Kofi Annan, calling for Saddam to be tried in Iran.
"Iran's public opinion wants Saddam Hussein to be prosecuted at a fair court in the Islamic Republic of Iran," it quoted part of the letter as saying.
Iraqi Governing Council members on Sunday indicated Saddam would be put on trial in Iraq under a new tribunal system set up last week to try Saddam and fellow Baathist leaders.
Iran has long-standing war reparations claims of tens of billions of dollars against Iraq for the bloody war which Saddam launched in 1980.
The country has welcomed the capture of Saddam, described by Ramazanzadeh as "one of the biggest criminals of this century".