The liberal Democratic Party's presidential candidate, Moon Jae-in, says if North Korea continues to launch missiles and goes ahead with a sixth nuclear test, it will be crossing a bridge of no return.

During a visit to the Air Force Operations Command in Pyeongtaek, Gyeonggi Province on Friday, Moon said he wants to issue a warning that if the provocations continue, the North will be further isolated from the international community and subject to stronger sanctions. 

The presidential hopeful added it could also be difficult to maintain the Kim Jong-un regime. 

Moon explained his stance of a two-track approach on North Korea, including stringent sanctions and pressure alongside negotiations and dialogue.

But he stressed if Pyongyang proceeds with another nuclear test, inter-Korean dialogue will be impossible for a considerable time.

Moon promised efforts for South Korea to one day stand on its own in terms of national defense through modernized and more scientific combat power, and vowed to increase the defense budget from the current two-point-four percent of gross domestic product(GDP) to three percent over the long term.

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