Seoul: US President Barack Obama's top ambassador for North Korea urges Pyongyang to engage in dialogue with Washington to defuse nuclear tensions while warning of "consequences" if the regime pushes ahead with a threatened atomic test.

Ambassador Stephen Bosworth arrived on Friday in Seoul from Beijing just hours after North Korea accused the Obama administration of harbouring a hostile policy toward Pyongyang, saying it would further bolster its nuclear arsenal in response.

North Korea's Foreign Ministry said in a statement carried by state media on Friday that "nothing would be expected from the US, which remains unchanged in its hostility toward its dialogue partner."

Bosworth said Washington is ready and willing to hold direct talks with Pyongyang.