US Secretary of Defense James Mattis warned North Korea on Friday (3 February) that Pyongyang would face an "effective and overwhelming" response if it used its nuclear weapons.

The defence chief, who is currently on a visit to its ally South Korea said: "North Korea continues to launch missiles, develop its nuclear weapons programme and engage in threatening rhetoric and behaviour. Any attack on the United States, or our allies, will be defeated, and any use of nuclear weapons would be met with a response that would be effective and overwhelming."

The Pentagon said in a statement that the US remains "steadfast" in its "ironclad" commitment to defend South Korea.

Mattis's warning to Pyongyang comes as Kim Jong-un's regime continues to ramp up tension in the Korean peninsula by threatening to carry out missile and nuclear tests. In 2016, Pyongyang conducted at least 20 missile tests and two nuclear detonations, defying UN regulations.

Meanwhile, South Korean Defence Minister Han Min-koo said: "Faced with a current severe security situation, Secretary Mattis' visit to Korea ... also communicates the strongest warning to North Korea."

In January, Kim's regime had said that the country was close to test-launching a long-range ballistic missile.

Additionally, US-based think tank 38 North – which monitors North Korea's activities – has cautioned that Pyongyang is believed to have resumed operations at its Yongbyon nuclear facility. The plant produces plutonium, which can be used for its nuclear weapons programme, Reuters reported.

Repeated threats from Pyongyang have forced Seoul and Washington to step up their defences against North Korea, which led the US to initiate the installation of the Terminal High Altitude Area Defense (Thaad) missile defence system in South Korea.

However, China raised objections to the deployment and said that the anti-missile system's radar could penetrate its territory. Mattis reassured China and said: "No other nation needs to be concerned about Thaad other than North Korea".

Hwang Kyo-ahn James Mattis
US Defense Secretary James Mattis (L) shakes hands with South Korea's acting President Hwang Kyo-ahn prior to their meeting at the Government Complex in Seoul, South Korea on 2 February 2017REUTERS/Song Kyung-Seok/Pool