The 70-year-old entrepreneur Guillermo Botero, a lawyer by profession, has no experience in security matters.

"We're going to have a new defense minister, a defense minister with great management experience," said Duque, who is due to take over on August 7 from Juan Manuel Santos, who was awarded the Nobel Peace Prize for negotiating the deal with FARC.

Duque has vowed to be tough on crime but has caused tensions with the former FARC guerrillas, who were transformed into a political party after the December 2016 pact that included the disarmament of 7,000 Marxist fighters.

Upon his election last month, Duque vowed to make "corrections" to the peace deal, criticizing it for being too lenient towards former rebels.

The FARC responded by imploring Duque to show "good sense" but on Monday former rebel leader Ivan Marquez said he wouldn't be taking his seat in Colombia's Senate -- as agreed in the pact -- citing "modifications" to the deal as one of his reasons.

Botero, president of the National Traders' Federation, has been especially critical of the pact's prevision for sanctions against ex-guerrillas and fighters accused of crimes committed during the half-century conflict.

The agreement stipulates that former fighters who confess to their involvement in atrocities can avoid prison.

Botero will be tasked with organizing the fight against the remnants of dissident left-wing rebels still fighting the government, as well as various drug trafficking cartels.

He must also tackle the issue of the murder of human rights activists -- at the staggering level of one every three days, since the start of the year.