In a joint press conference with Foreign Affairs Secretary Perfecto Yasay, Kerry mentioned his concern over the protection of people's rights amid the authorities' aggressive means to uphold peace and order.
"I made very clear that civil and human rights need to be protected even as we work to keep our society safe," Kerry told the Inquirer.
On the same page as Kerry is Vice President Leni Robredo, who raised concern over the rampant drug-related killings under the new administration.
However, she said she still believes in upholding human rights through providing due process.
"Ito yung buod, ito yung core din ng pinakakaluluwa ng ating bansa. Kung naaalala natin...galing tayo sa isang rehimen na hindi binigyan ng malaking diin yung human rights, kaya [naging] malaking bahagi [ito] ng ating Konstitusyon," she told GMA News Online.
Kerry and Robredo's statements came in response to the "relentless" war on drugs by which already saw more than 300 people killed in the past month.
Thousands of arrests have also been made alongside the numerous mass surrenders of drug suspects since Duterte took office.