Ramsey Clark, a former US attorney general, also complained that the former leader could not receive a fair trial in such a climate of fear.
"There are few facts that could greater inflame passions and divide irreconcilably the people of Iraq than a conviction and severe punishment, especially execution, of President Saddam Hussein," Clark said.
Speaking to Reuters in Jordan before flying to Baghdad for the resumption of the five-month-old trial on Sunday, he said the proceedings had stirred up hatred between Iraq's communities, pushing Sunnis and Shi'ites closer to civil war.
"It creates sectarian passions that destroy rationality and reason and the search for truth," said Clark, an outspoken critic of the United States for organising the trial.
Saddam and seven others are being tried for crimes against humanity in connection with the deaths of 148 Shi'ite men from the village of Dujail following a failed attempt on Saddam's life there in 1982.
'Climate of fear'
"There is not a person who feels secure," Clark said of the trial. "It's impossible to hold a fair trial in such a climate ... A trial is supposed to be a rational process. Fear is the ultimate irrationality. How do you function in fear?"
Saddam and seven others are tried
for crimes against humanity
Two of Clark's colleagues on the defence team were shot dead after the trial began in October. Clark has walked out of the proceedings several times to protest against the behaviour of the judges and the chief prosecutor.
The Shi'ite- and Kurdish-led interim government has urged a rapid conviction and hanging for Saddam, whose Sunni-dominated administration frequently oppressed both those communities.
Clark indicated that the defence would seek to justify the actions taken against those accused of trying to assassinate Saddam, following an admission by the ousted president last week that he ordered the trials that led to their executions.
"He owes it as president that he should take responsibility"
Ramsey Clark, Saddam Hussein's American lawyer
A US official involved with the court called that a "damning admission" after testimony over the previous months from witnesses who recounted tales of torture, but gave little evidence directly linking Saddam to the men's deaths.
Clark said that documents presented by the prosecution showing Saddam's signature on 1980s trial papers reinforced the defence argument that a proper judicial process was followed.
"He owes it as president that he should take responsibility," Clark said of Saddam's admission. The former leader himself told the court on 1 March: "Where is the crime?"
Clark said the defence would point out that in 1982, when gunmen from the Shi'ite Dawa party tried to kill Saddam in Dujail, Iraq was at war with Shi'ite Iran:
Saddam's lawyers suspect chief
judge Abdel-Rahman's nuetrality
"It was at a time of war and involved loyalty to the enemy with people who were Iraqi supporting Iran," he said.
He complained of practical difficulties in preparing the defence case: "You have to go to the scene before you ever try to cross-examine a witness," he said. "How can we go to Dujail right now? We couldn't survive. We have to have protection."
Clark said he was still seeking to have the chief judge removed because of suspicions of bias stemming from his origins in the Kurdish town of Halabja, scene of a gas attack in 1988 that will feature in a likely future trial.