The US Defence Secretary James Mattis has warned North Korea it would be an "effective and overwhelming" response from the US if it used nuclear weapons. According to The Guardian, James Mattis reassured the South Korean government in Seoul that the US would retaliate if northern neighbor launches any attack.

The US Defence Secretary Mattis's remark comes amid concern that North Korea could be readying to test a new ballistic missile. That could be an early challenge for Trump's administration.

According to the U.S think-tank 38 North, North Korea, this regularly threatens to destroy South Korea and its main ally, the United States. They have conducted more than 20 missile tests last year, as well as two nuclear tests.

BBC has reported that as a post -war defense deal the US has a considerable military presence in South Korea and Japan. The US has 28, 5000 US troops in South Korea, mostly ranged along the heavily armed border separating it from North.

However, president Donald Trump has pointed out that he wants both South Korea and Japan to pay more towards maintaining that presence. In the recent visit, Mattis reassure south Korea that Trump administration "remains steadfast" in its "iron-clad" defense commitment.

North Korea's actions have promoted the United States and South Korea to respond by bolstering the defense. Under the Obama administration, the US and South Korea agreed to deploy a US-made Terminal High Altitude Area Defence (THAAD) missile defense system in South Korea.

However, China has objected to THAAD, saying this step put the direct threat to China's own security. That will do nothing to bring North Korea back to the negotiating table, leading to calls from South Korean opposition leaders to delay or cancel it.

Meanwhile, the official from US defense secretary said the united States essentially have two options. First to curb North Korea's fast-expanding nuclear and missile programs-negotiate or take military action.