North Korea threatened "merciless punishment" on US President Donald Trump over "foolish remarks" on Sunday, two days before his state visit to South Korea.

The Rodong Sinmun, the main newspaper and organ of the ruling Workers' Party of Korea, published a commentary accusing Trump of "seriously stimulating" North Korea with his words.

Trump kicked off his Asia tour in Japan earlier Sunday. He's scheduled to land in South Korea on Tuesday for a summit with President Moon Jae-in during his two-day visit.

Trump has engaged in a war of words with North Korean leader Kim Jong-un, referring to Kim as "Little Rocket Man" and threatening to "totally destroy" North Korea.

In the report carried by the Korean Central News Agency, Rodong Sinmun argued Trump must heed assertions from other US experts that he must "halt the reckless blackmail and take hands off the Korean affairs."

"Nobody can predict when Trump does a reckless act. The only and one way for checking his rash act is to tame him with absolute physical power," the report said in English. "If the US misjudges (North Korea's) toughest will and dares to act recklessly, the latter will be compelled to deal a resolute and merciless punishment upon the former with the mobilisation of all forces. The US has no energy to prevent it. Then its regret is too late."

Trump defended his tough rhetoric on North Korea after landing in Japan on Sunday. Addressing the US troops here, Trump said, "No one, no dictator, no regime should underestimate American resolve."

As for the US policy on Pyongyang, Trump said, "There's been 25 years of total weakness and so we're taking a very much different approach." (Yonhap)