Iraqi president Jalal Talabani is refusing to sign the execution order for Tariq Aziz, former deputy prime minister under Saddam Hussein.
Aziz, 74, was condemned to death last month by an Iraqi court for persecution of religious parties.
Mr Talabani told France 24 television he would never sign the order because of Aziz's age and because he is an Iraqi Christian.
The president is known for his general opposition to the death penalty.
Our correspondent in Baghdad, Gabriel Gatehouse, said that in 2006 Mr Talabani refused to sign a warrant ordering the execution of Saddam Hussein.
Instead, the order was ratified by one of Mr Talabani's two deputies, and the former Iraqi president was hanged all the same.
It is not clear what will happen in this case.
Iraq is in the middle of a drawn-out process of government formation.
Our correspondent says the constitution requires executions to be ratified by the presidency, and carried out within 30 days of the sentence being confirmed.
Mr Talabani was re-appointed last week after more than eight months of political wrangling. At the moment, he has no formal deputies who could authorise the death penalty in his place.
As Iraq's foreign minister, as well as deputy prime minister, Tariq Aziz was the face and voice of Saddam's government on the world stage.
He had been previously convicted for his role in the execution of dozens of merchants for profiteering and for his role in the displacement of the Kurdish minority in northern Iraq.
He is also reported to be seriously ill.
The European Union, the Vatican and Russia have called on Iraq not to execute Aziz on grounds of age and ill health.
When he was sentenced last month, the BBC's Jim Muir says, Aziz was not widely seen as one of Saddam's evil insiders, and a lobby could spring up to prevent him being sent to the gallows.