Iraq's prime minister says former President Saddam Hussein will be handed to Iraqi legal custody on Wednesday and charged the following day.
Saddam's lawyers want an independent medical assessment
The announcement comes a day after the US-led coalition handed power to Iyad Allawi's interim government.
Iraqi officials say the charges against the ex-leader are likely to include crimes against humanity and war crimes.
Earlier three US troops were killed in a roadside bomb attack in Baghdad - the first combat deaths since the handover.
In other developments:
- A US soldier missing in Iraq since April is reported shot dead by his captors
- three Turks kidnapped last week are released
- rocket-propelled grenades are reportedly fired at a police station south of Baghdad, killing two Iraqis
- new US ambassador John Negroponte, along with
Neil Mules of Australia and Torben Getterman of Denmark, present their credentials to the new Iraqi leadership in separate ceremonies.
Saddam Hussein, who was captured by US forces near his hometown of Tikrit in December, will remain in a US-run jail until Iraqi detention services are ready to take physical custody.
He will not face trial for several months, but could go before a judge as early as Thursday, Mr Allawi said.
The BBC's John Simpson in Baghdad says the interim prime minister has forced the Americans' hand by insisting on the handover.
Washington had reacted frostily to the idea when it was first suggested earlier this month, he says, but could not refuse without doing serious damage to Mr Allawi's authority.
Eleven other top detainees will be handed over, including former Deputy Prime Minister Tariq Aziz, Ali Hassan al-Majid - known as "Chemical Ali" - former Vice-President Taha Yassin Ramadan, and two of Saddam Hussein's half-brothers.
Tariq Aziz - Deputy PM
Taha Yassin Ramadan - Vice-President
Sultan Hashim Ahmad al-Tal - Defence Minister
Ali Hasan al-Majid - "Chemical Ali"
Watban Ibrahim Hassan al-Tikriti - Saddam Hussein's half-brother - intelligence minister
Saddam Hussein is expected to face war crimes charges over the 1990 invasion of Kuwait and subsequent suppression of Shia and Kurdish uprisings, the use of chemical weapons against the Kurds in 1988 and the
1980-1988 Iran-Iraq war.
But the Iraqi official preparing cases against the men, Salem Chalabi, told the BBC that arrest warrants had only just been issued for the accused and charges had not yet been finalised.
Some indictments would be brought in the autumn of this year, but not for the top people on the list, he said.
A member of Saddam Hussein's legal team, Giovanni di Stephano, told the BBC they would prepare his defence once the charges against him were made clear.
The lawyer demanded access to his client and an independent medical assessment to see if he was fit to stand trial.
Iraq's interim interior minister told the BBC he believed the security forces could win public confidence by tackling terrorism and organised crime - something he said American-led forces had largely failed to do.
Falah Hassan Al-Naqib said the government would not hesitate to introduce emergency security measures if they were required, but that no decision had yet been made to do so.
The interim government has been empowered to conduct the day-to-day running of Iraq, but its existence is guaranteed by the presence of a multinational force led by about 138,000 US forces.
The handover of power had been due to take place on Wednesday, but a hurried and secret ceremony was held on Monday between outgoing civil administrator Paul Bremer, Mr Allawi and several figures of the new interim government.
At a second ceremony in the afternoon - broadcast
live on Iraqi TV - the interim government was sworn in and Mr Allawi urged all Iraqis to unite against "foreign
terrorists who are killing our children and destroying our