"Tariq Aziz told me that he will not take the witness stand against Saddam," Badi Arif Izzat said on Thursday.
The lawyer said that Aziz, who has been in US custody since his surrender in the immediate aftermath of 2003 US-led invasion, had had no opportunity to see the ousted president.
The 11 senior aides currently in custody are incarcerated together and able to see each other for three hours a day but Hussein himself was being held separately, Izzat said.
Iraqi officials have said that Hussein is being held in Camp Cropper, a US base at Baghdad airport, but Izzat said he did not know exactly where the others were being detained as he had been taken there in a US armoured personnel carrier.
Aziz, an English-speaking Christian and former foreign minister who was the ousted government's best known spokesman to the outside world, remained "in good health and spirits" despite his 20-month detention, the lawyer said.
In October, there were a flurry of rumours that Aziz, who was born in 1936, had died in custody, although they were later comprehensively denied.
Saddam is being held separately
from his former senior aides
On 1 July, Aziz was formally charged alongside his captive colleagues by the Iraq Special Tribunal established by the US-led coalition to try senior members of the former government.
He was charged with two counts of mass murder, allegedly committed in 1979 and 1991, both punishable by death if he is found guilty.
Izzat said Aziz insists on his innocence and wants to call longtime information minister Muhammad Said al-Sahhaf and military intelligence chief Sabir Abd al-Aziz al-Duri as defence witnesses.
"Any accusation of my involvement in this affair is baseless," the lawyer quoted him as saying.
Aziz insists he could not have had any part in the suppression of Kurds immediately after the 1991 Gulf war, as alleged by the prosecution, as he was still foreign minister at the time and divided his time between Baghdad and Arab capitals.