International Desk: US President Donald Trump's defense secretary James Mattis warned North Korea on Friday of an "effective and overwhelming" response if Pyongyang chose to use nuclear weapons, as he reconfirmed Seoul of steadfast US support at the end of a two-day visit.
North Korea's repeated missile and nuclear tests and aggressive statements go on to alarm and anger the region.
The US has a considerable military presence in South Korea and Japan, as part of a post-war defense deal.
President Donald Trump has previously said he wants both countries to pay more towards maintaining that presence.
Mr. Mattis has been using his visit to reassure South Korea that the Trump administration "remains steadfast" in its "iron-clad" defense commitments to the region, said the Pentagon.
Speaking after talks at the defense ministry with his South Korean counterpart Han Min-koo, Mr.
Mattis told media that "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".
North Korea conducted its fifth test of a nuclear device last year and claims it is capable of carrying out a nuclear attack on the US, though experts are still unconvinced its technology has progressed that far.
It has also said it recent weeks that is has a new intercontinental ballistic missile, capable of reaching the US mainland, which it is taking preparation to test launch at any time.