By Mike McDonald

GUATEMALA CITY (Reuters) - Lawyers for Guatemala's ex-dictator Efrain Rios Montt, on trial for genocide, began their defense on Tuesday with testimony that the former strong man did not direct specific military operations during his 1982-1983 rule.

Carlos Leonel Mendez, a former Guatemalan army engineer and first witness to testify for the defense since the trial opened last month, said battlefield operations were not part of presidential powers during the country's bloody civil war.

Mendez noted the president's military powers were limited to mobilizing troops and promoting soldiers to higher ranks, and that Rios Montt obeyed those laws during his 17-month rule.

"Considering the abuses of previous presidents, Congress at that time limited the president's functions to mobilizing and demobilizing troops, promoting troops to the grade of colonel and awarding decorations," said Mendez.

Rios Montt, 86, was ordered to stand trial for genocide and crimes against humanity in January after evidence linked him to the killing of more than 1,700 indigenous people in a counterinsurgency plan carried out under his command.

The trial marks the first time a country has prosecuted one of its former heads of state on such charges.

Rios Montt's defense team has argued that genocide never happened in Guatemala since indigenous peoples also formed part of the armed forces during the country's 1960-1996 civil war and that he did not control battlefield operations.

Mendez said the president is part of the army's high command, but that command does not direct the military.

"The president sends orders to all his ministers. The defense minister sends orders to the chief of the army's central base, who defines the strategies to send to the field units," said Mendez, who is now a lawyer.

The war pitted leftist insurgents against a string of right-wing governments. Some 200,000 people died in the conflict, many of them ethnic Maya, and another 45,000 disappeared.

Rios Montt dissolved Congress and the country's constitution when he assumed power in a bloodless coup in March 1982.

He has yet to take the stand in his own defense.

(Reporting by Mike McDonald; Editing by Todd Eastham)