A retrial in Guatemala of a former dictator accused of genocide, Efrain Rios Montt, that was supposed to start Monday has been suspended following defense challenges, lawyers for both sides said.

The Guatemala City court that was to hear the matter behind closed doors "decided to suspend the start of the trial of general Rios Montt because of three pending petitions to resolve," one defense lawyer, Jaime Hernandez, told reporters at the court house.

The Central American country's constitutional court in 2013 ordered the retrial after overturning Rios Montt's conviction and 80-year prison sentence on the same charges.

The new trial was to take place without the presence of 89-year-old Rios Montt, who is said to be senile and bedridden in his home in a wealthy district in the capital.

Rios Montt ruled Guatemala in 1982 and 1983 at the head of a military government. His reign took place at the height of a bloody 36-year civil war that ended in 1996.

He is accused of being responsible for the murders of 1,771 indigenous Mayan Ixils. His lawyers claim the allegations are "political" and in any case their client is now incapable of understanding the charges against him.

According to the United Nations, some 200,000 people died or were made to disappear during Guatemala's long, brutal conflict.

Hernandez said one of the petitions delaying the start of the retrial argued that Rios Montt was too senile for it to go ahead.

Another sought the recusal of a judge who sat on the initial 2013 trial.

And the third wanted to separate his case from the public trial of his intelligence chief, which was supposed to take place at the same time under the same court.

Rights activists and the families of those killed have been hoping for a fresh conviction against Rios Montt.

Amnesty International has said the trial was a "major test" for Guatemala's justice system and an opportunity for it to show its commitment to upholding human rights.

Hector Reyes, a lawyer for the Human Rights Legal Action Center that is one of the plaintiffs, said: "We fear that the defense is using legal delaying methods and that this trial ... will end up being cancelled."

If that happened, he said, "it would be a revictimization of our victims."