South Korean President Moon Jae-in on Monday urged both North Korea and the United States to act reasonably and peacefully, saying the North Korean nuclear and missile issues must be resolved peacefully under any circumstances.

"I urge North Korea to immediately stop all provocations and threats, and stop making the situation worse," Moon said during a weekly meeting with his top aides at the presidential office Cheong Wa Dae.

"I say this again with a strong emphasis. The national interest of the Republic of Korea comes before anything else. The national interest of the Republic of Korea is peace," he added, according to Cheong Wa Dae pool reports.

Moon's remarks come amid a heated exchange of threats between the communist North and the United States, Seoul's strongest ally that also maintains some 28,500 troops in South Korea.

In its latest provocation, Pyongyang said it may consider staging a missile launch exercise around the US-controlled island of Guam, a threat that Washington says will be met by "fire and fury" that the world has never seen before.

Moon clearly voiced his opposition to any armed conflict.

"We cannot have a war on the Korean Peninsula ever again."

He apparently sought to calm the US down, saying the Korea-US alliance was aimed at defending peace.

"I am confident the United States too will react calmly and responsibly to the ongoing situation under the same basic stance as ours," he said.

"Peace on the Korean Peninsula will not come by force. Even if peace and negotiations require pain and patience, we must do so."

The South Korean leader also promised a better future for the North should the latter chose what he called the right path.

"If North Korea makes the right decision, we will work together (with North Korea) to ensure the bright future of our nation by greatly expanding and improving inter-Korean exchanges," he said.

The South Korean leader also sought to assure his own people amid growing concerns of an armed conflict here.

"I promise the people. The crisis is being safely managed. We are also making all necessary preparations for any possible event. We will build a Korean Peninsula of peace and prosperity together with the people," he said. (Yonhap)