North Korea is threatening to introduce a new nuclear deterrent because of United States hostility, as tensions continue over a sunken South Korean warship.
Pyongyang has also accused the US and South Korea of bringing heavy weapons into the demilitarised zone between the two countries, the BBC reports.
The North Korean news agency says strong military counter-measures will be taken in the area if the weapons are not withdrawn.
The statements came hours after US President Barack Obama urged his Chinese counterpart to take a stronger stance on the sinking of the Cheonan in March.
Forty-six sailors died when the South Korean ship split in two and went down near the disputed inter-Korean maritime border.
An international team of investigators found North Korea sank the warship with a torpedo. South Korea is seeking a UN Security Council response over the incident, for which North Korea denies all responsibility.
The US president says he's had blunt talks with China's President Hu Jintao on the issue and hopes President Hu will recognise the incident was an example of North Korea overstepping the line.
