GUATEMALA CITY (AFP) - The genocide trial of Guatemala's former dictator Efrain Rios Montt has been scheduled to resume Jan 5, 2015, authorities said.

The still distant date "is due to the crammed agenda of the court," said Mr Hector Reyes, an attorney for families of victims.

Rios Montt, now 87, went on trial in March on charges of ordering the massacre of indigenous Ixil Maya people in the 1980s as part of a scorched-earth policy in the most brutal chapter of a 36-year civil war that ended in 1996.

He was convicted on May 10, 2013 of genocide and war crimes in a historic ruling and got an 80-year sentence.

However, that same month, the Constitutional Court struck down the conviction and the sentence on grounds the ex-dictator was denied due process.

The ruling, by three votes to two, essentially rolls back the trial to a point at which it stood on April 19, 2013 when it was temporarily suspended by the court to consider a defense motion.

The same judges that found Rios Montt guilty were expected to resume the trial.

"As lawyers, we certainly see this as pushing back for a long time justice for victims, and that the case should be resumed" earlier, Mr Reyes argued.

Rios Montt's conviction had made him the first Latin American ex-dictator to be convicted of genocide - defined as a systematic attempt to exterminate an entire people for political, racial, religious or other reasons.

His alleged crimes occurred during a brief but particularly gruesome stretch of a war that started in 1960, dragged on for 36 years and left around 200,000 people dead or missing, according to a 1999 UN-sponsored report.