US warns N Korea it is skating "dangerous line" with expected missile launch

The United States has warned North Korea it is skating a "dangerous line" with an expected missile launch that could start a whole new cycle of escalating tensions in a region already on a hair-trigger, AFP reports.

South Korean and US forces remained on heightened alert Thursday with both experts and officials suggesting a launch was likely in the build-up to April 15 birthday celebrations for the North's late founder Kim Il-Sung.

It might also coincide with visits by US Secretary of State John Kerry and NATO chief Anders Fogh Rasmussen, who will both be in Seoul on Friday.

"North Korea... with its bellicose rhetoric, its actions, has been skating very close to a dangerous line," US Defense Secretary Chuck Hagel said Wednesday.

"Our country is fully prepared to deal with any contingency, any action that North Korea may take or any provocation that they may instigate," Hagel added.