North Korea’s official Rodong Sinmun newspaper denounced South Korea’s plans to purchase PAC-3 interceptor missiles from the U.S., threatening to build its nuclear program in response.

The editorial published on Sunday said that the weapons sale, approved by the U.S. government earlier this month, is sure to spark an “arms race” and “only compels the DPRK to further bolster its nuclear deterrence.”

The $1.405 billion sale of 136 Patriot Advanced Capability (PAC)-3 missiles, now in its preliminary stage, is part of Seoul’s plan to upgrade its current PAC-2 missile defense system by 2020. In 2008, South Korea bought 48 second-hand