US Defence Secretary James Mattis has warned North Korea that any use of nuclear weapons on America or its allies will be met with an "effective and overwhelming" response.

Mr Mattis was speaking from South Korea at the end of a two-day visit, during which he reassured Seoul of America's support.

He said: "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,"

Image: Defence Secretary James Mattis has warned of the 'overwhelming' capabilities of the US

North Korea's autocratic leader Kim Jong-un regularly issues threats of destruction against its neighbour and the US.

There are 28,500 US troops permanently based in South Korea and a further 50,000 in Japan.


The secretive Communist nation conducted more than 20 missile tests last year along with two nuclear tests, despite UN resolutions and sanctions.

Image: Mr Mattis met his South Korean counterpart Han Min-Koo in Seoul

There are fears that North Korea could be preparing a new ballistic missile.

This would be become Donald Trump's first test on the issue, just weeks after becoming US President.

But during an appearance with his South Korean counterpart Han Min-koo, Mr Mattis said the US commitments to "defending our allies and to upholding our extended deterrence guarantees remain ironclad".

Mr Han said North Korea's actions "blatantly threaten" the international community and have created "a severe security situation" on the peninsula.

The visit to South Korea is Mr Mattis's first overseas trip since beginning his new role on 20 January.

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Mr Mattis also discussed a timetable for the deployment of an advanced US missile defence system intended to boost the protection of South Korea and Japan.

The current caretaker leader of South Korea supports the plan, but the country is approaching national elections.

He found himself having to reassure the South Koreans of the US commitment to a defence treaty that his president had described as a bad deal while campaigning.

Mr Trump had even suggested that South Korea and Japan should get their own nuclear weapons instead of relying on the US.

Mr Mattis heads to Tokyo today.