Rios Montt was president in the early 1980s

Mr R�os Montt, who took power in a coup in 1982 and governed for 18 months, is currently president of Congress.

His opponents say he is barred from becoming a presidential candidate because the constitution forbids former coup leaders from running for president.

But supporters of the former military leader say the constitution was adopted in 1986 and can't be applied retrospectively.

Mr Rios Montt, 77, was elected by 250 delegates at party meeting, held in a sports stadium in Guatemala City.

"I accept the challenge of being a presidential candidate with tranquility and humility,"he said.

Agricultural Minister Edin Barrientos was chosen to be his running-mate.