Saddam Hussein's sentence must be carried out within 30 days
Chief defence lawyer Khalil al-Dulaimi said Saddam was a prisoner of war and should not be handed to his enemies.
The former leader could be hanged on any day over the next four weeks, after an appeal against his execution failed.
The Vatican has condemned the sentence, saying it was wrong to answer crime with another crime.
The sentence is for killings in the town of Dujail in the 1980s. A trial for a second case continues.
"I ask all international organisations, the United Nations, the Arab League and world leaders, to intervene urgently with the American administration to prevent Saddam being handed to the Iraqi authorities," Mr Khalil al-Dulaimi told AFP news agency.
"Saddam is a prisoner of war and according to international law he should not be handed to his enemies," he added.
Meanwhile, a senior Vatican official, Cardinal Renato Martino, told Italy's La Repubblica newspaper that life should be protected from conception to natural death, and that execution was not a natural death.
He said there was no doubt that Saddam Hussein was guilty of mass murder.
However, he hinted that he hoped for clemency in the 30 days before the sentence had to, by law, be carried out.
Saddam Hussein is being held in US military custody near Baghdad.
In a letter written from his prison cell, he said he was ready to die as a "sacrifice" for Iraq.
He urged his countrymen to unite against enemies and said his death would make him a "true martyr".
His lawyers, who released the message, said it was written on 5 November, the day an Iraqi tribunal sentenced him to death for ordering the killings of scores of Shia Muslims in Dujail.
The former leader is on trial separately in connection with a military campaign against Kurdish communities in the 1980s.
However, under Iraqi law, he must be executed regardless of the second trial.
The time and location of the hanging has not been made public.
It may only be revealed after the former president is dead in order to avoid civil disruption and unrest.