Seoul, Aug 15 (IANS): South Korean President Moon Jae-in on Tuesday vowed to "prevent a war at all costs" amid the ongoing tension between Washington and Pyongyang.

"The government will prevent a war at all cost. We must peacefully resolve the North Korean nuclear issue no matter how many ups and downs there are," Moon said during the Kwangbok-jeol ceremony in Seoul, which celebrates South Korea's National Liberation Day and the end of 35-years of Japanese colonial rule in 1945.

Moon's promise came at a time of heightened tension between the US and North Korea, which earlier in August threatened with a plan to launch four missiles towards areas close to Guam, where important American military bases are stationed.

Pyongyang, however, apparently toned down its threats on Tuesday as Kim Jong-un reportedly decided to observe US behaviour "a little more" before undertaking the attack, according to North Korea's official KCNA news agency.

Moon reiterated that South Korea will not allow the US to carry out a pre-emptive strike against North Korea.

"Military action on the Korean Peninsula can only be decided by the Republic of Korea and no one may decide to take military action without the consent of the Republic of Korea," he said.

"At the same time, we will keep our doors open for a military dialogue" the President said, referring to the offer he made to Pyongyang in July.

The President also wanted to provide assistance to Pyongyang, claiming that Seoul does not want "the collapse of North Korea" and that his government will not pursue " reunification by absorption".