MONS, Belgium — Afghan forces will soon start taking charge of security for three quarters of the nation’s 28 million people, NATO’s top military commander said today, a milestone as the country assumes the lead for protecting the majority of its population.

Adm. James Stavridis also insisted the training of the Afghan army and police is proceeding well, despite attacks in which Afghan soldiers have turned their weapons on their U.S. and NATO partners.

“Very shortly we will announce further transition that will encompass 75 percent of the population,” Stavridis said. He did not elaborate on the exact timing of the announcement.

NATO leaders will meet in Chicago in May to map out a strategy to support the Afghan security forces after the withdrawal of most allied troops at the end of 2014. NATO forces have already handed over authority for about half the population.

This is the first public prediction that after the third phase occurs Afghan security forces will be assuming the lead for protecting the majority of the population.