In his first public remarks abroad as US defence secretary, James Mattis on Thursday criticised North Korea for provocative acts that he said required new consultations with traditional allies Japan and South Korea.
Mattis said he would speak with his Japanese and South Korean counterparts about new steps that might be needed to deal with North Korea's nuclear and missile threats.
The new Pentagon chief said his Seoul meetings would include discussion of deploying the US missile defence system known as THAAD or Terminal High Altitude Area Defense.
"I will talk to them about THAAD absolutely," Mattis said.
South Korea and the United States say the deployment of THAAD is designed to protect against North Korea's growing nuclear and ballistic capabilities.
The North appears to have restarted operation of a reactor at its main Yongbyon nuclear facility that produces plutonium that can be used for its nuclear weapons program, according to US think tank 38 North.
Regional power China has objected to THAAD, saying it will destabilise the northeast Asia security balance.
TRT World spoke to Carl Thayer from the University of New South Wales in Australia about Mattis's visit.