SEOUL, Feb. 3 (Xinhua) -- U.S. Defense Secretary James Mattis said Friday the Terminal High Altitude Area Defense (THAAD) anti-missiel system will be deployed in South Korea to protect its ally and U.S. forces stationed there.

The controversial THAAD deployment has drawn sharp criticism and strong opposition from China and Russia as its X-band radar can peer deep into the territories of the two countries, breaking strategic balance and bolstering arms race in the region.

Meanwhile, South Koreans have also held a series of protests against the deployment.

In his speech before holding talks with his South Korean counterpart, Defense Minister Han Min-koo, Mattis claimed that the Democratic People's Republic of Korea (DPRK) is continuing threatening rhetoric and actions as well as missile launches and the development of its nuclear program.

He said the United States will take defense measures, including the deployment of THAAD in South Korea to protect the U.S. troops there and the South Korean people.

The retired four-star Marine general arrived here Thursday on his first overseas trip since he took office about two weeks earlier. He will then visit Japan for two days.

The THAAD system is designed to shoot down incoming missiles at an altitude of 40-150 km, but most of DPRK missiles fly at an altitude of less than 40 km.

Seoul and Washington announced an abrupt decision in July last year to install one THAAD battery in southeast South Korea by the end of this year. Local media speculated that the installation can be completed between May and July.

Major presidential contenders in the South Korean opposition bloc demanded the THAAD deployment decision to be cancelled or delayed to the next government as President Park Geun-hye was impeached in December.