Satellite imagery of a North Korean facility indicates that Pyongyang is preparing for as many as two nuclear tests.
Concerns about a nuclear test followed the December launch of a long-range rocket from North Korea that orbited a satellite. Similar launches in 2006 and 2009 coincided with North Korean nuclear tests.
A statement Tuesday from the Minju Chosun newspaper of the North Korean Cabinet warned it would "ruthlessly strike" the United States if it's nuclear facilities were targeted in a pre-emptive strike, reports South Korean's Yonhap news agency.
The latest rhetoric from Pyongyang suggested a possible nuclear test was part of its anti-U.S. policies.
"If the Democratic People's Republic of Korea continues its provocative behavior and takes further steps, that there must be further consequences (as outlined in Security Council resolutions)," she said.