The Estado Mayor Central armed group was founded by former members of the Revolutionary Armed Forces of Colombia (FARC) rebels who did not join that group's demobilization and conversion to a legal political party.

Petro has vowed to end Colombia's 60-year conflict - which has killed at least 450,000 people - by inking peace or surrender deals with remaining rebels and crime gangs and by fully implementing the FARC accord.

"The attorney general of the nation, after weighing the arguments presented by President Petro, and in accordance with his legal and constitutional duties, has decided to suspend existing and future arrest warrants against 19 people," the attorney general's office said in a statement.

None of the 19 have extradition warrants, the prosecutor's office said.

The suspension will allow discussions to take place between the dissidents and government officials, Petro said on Twitter - a first step to beginning formal talks.

"A second peace process is beginning," Petro tweeted, adding discussions would be established between the government and the group.

The government is already in peace talks with the National Liberation Army (ELN) rebels and the two sides have said they are progressing toward a bilateral ceasefire deal.

The country's top peace official told Reuters last month the government expects talks with the Estado Mayor and Segunda Marquetalia, another FARC dissident group, within weeks.

The government is holding a ceasefire with the dissident groups and some crime gangs, though Petro said on Thursday that the Clan del Golfo criminal group had broken its deal.

The attorney general said in January he would not drop extradition warrants for drug-trafficking bosses, with whom Petro wants to agree surrender deals.