'Others could be emboldened by N Korea'

If the world fails to stop North Korea's nuclear program other countries might feel emboldened to pursue such weapons, Julie Bishop fears.

The foreign minister is warning against an increase in the proliferation of nuclear weapons if the rogue regime isn't diplomatically and economically isolated.

"A failure to enforce the resolutions and check North Korea's ambitions could embolden other nations to act illegally in pursuit of nuclear weapons and other weapons of mass destruction," she writes in Fairfax Media on Wednesday.

Labor's defence spokesman Richard Marles is in Washington DC and has had talks at the Pentagon and with members of Congress.

"A conflict with North Korea would see a war on a scale that has been unprecedented within our lifetime," he told Sky News.

"This is not the first option, where people's heads are focused, at least in their conversations with me ... is on peaceful means, diplomatic options."