Rios Montt is accused of being ultimately responsible for the murders of 1,771 indigenous Ixil-Maya people in 1982-1983, at the height of Guatemala's 36-year civil war which ended in 1996.
Now aged 89, he had been on trial in absentia since March 16 in Guatemala City. His attorneys say he suffers from dementia and is too ill to attend.
A May 2013 trial delivered a conviction and an 80-year sentence, but that was overturned days later by Guatemala's constitutional court, which ordered the new trial.
No date was given for when the retrial might resume.
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Other legal challenges still hanging over the retrial include one from Rios Montt's lawyers arguing that their client is too senile to be judged.
According to the UN, some 200,000 people died or were made to disappear during the Guatemala's long, brutal civil war.
Should he be convicted again, he would be subject to detention in line with his health condition, meaning possible hospital internment or home confinement.
Rios Montt in March 1982 deposed Lucas Garcia, who went on to die in exile in Venezuela in 2006 aged 81.