The US and South Korea have stressed their close relationship and confirmed they will deploy the Terminal High Altitude Area Defence (THAAD) missile defence system this year as scheduled, as speculation grew that North Korea is planning a mid-range rocket test.
US Defence Secretary James Mattis had a 30-minute phone call with South Korean defence minister Han Min-koo.
Mr Mattis, a retired Marine general, is scheduled to visit South Korea from Thursday to Friday, his first overseas trip since his appointment as defence secretary on January 20th.
"Secretary Mattis recognised the significance of the US-ROK (Republic of Korea) alliance, noted that his visit to the ROK and Japan will be his first overseas trip during his tenure as secretary of defence, and conveyed that the US will stand shoulder-to-shoulder with the ROK forces," Pentagon spokesman Capt. Jeff Davis said in a statement.
Washington maintains a significant troop presence of round 28,500 troops.
The US backed South Korea in the Korean War (1950-1953) which ended in ceasefire, but without a peace treaty, and has left both sides of the Korean peninsula in a tense stand-off for the past six decades.
There had been speculation that THAAD might be delayed because of ongoing political turmoil in South Korea, where President Park Geun-hye is facing impeachment.
On Friday Mr Mattis flies to Japan, another strong ally of Washington in Asia and where he spent part of his career as a Marine.
South China Sea
His visit comes at a time when relations between the US and China have been strained by President Donald Trump's hawkish comments on China's ambitions in the South China Sea, and growing closeness with self-ruled Taiwan, which Beijing considers its sovereign territory.
Both China and Russia oppose the deployment of THAAD as they believe the system can be used against their own missile systems and Beijing has said the system's powerful X-band radar can spy on its military activities.
Washington insists the system is purely defensive and exists solely to deter the nuclear threat from North Korea.
In his New Year’s Day address, North Korean leader Kim Jong-un threatened to test an intercontinental ballistic missile capable of reaching the US mainland.
Last year, Pyongyang conducted two nuclear tests and test-fired 24 ballistic missiles as part of its efforts to develop a long-range ballistic missile.
North Korea is believed to have restarted operation of a reactor at its main Yongbyon nuclear facility that produces plutonium for its nuclear weapons programme.
A missile test would be an early test of US President Donald Trump, who has criticised China for not doing enough to help counter the missile programme being developed by North Korea, an ally of Beijing.
The North has carried out a number of nuclear tests and missile launches in defiance of sanctions imposed by the UN Security Council, the toughest ever imposed on Pyongyang over its missile programme.
China has been wrong-footed by the North on its nuclear plans and has reluctantly backed United Nations sanctions.
In an editorial, the Chinese Global Times tabloid said THAAD meant South Korea has “fallen out with China, which strongly opposes the deployment and has implemented some countermeasures.”
“South Korea is a middle power, which is not only a fact, but also what it identifies itself as. As a middle power caught in the middle of four great powers, particularly China and the US, it is not easy to gain advantage from all sides,” the commentary said.
