North Korea claimed Tuesday that its rockets were able to hit the US mainland.
The warning comes just two days after an agreement between the US and South Korea allowing the latter to extend the range and payload of its ballistic missile systems.
GlobalPost reported that South Korea said over the weekend that it would triple the range of its rockets to penetrate anywhere inside its northern neighbor.
It is believed that North Korea is working on intercontinental ballistic missile systems that could strike the US.
North Korea is about 4,500 miles from the US coast.
The longest-range North Korean missile is believed to be the Musadan, which can strike targets nearly 2000 miles away.
The last two tests, however, likely disguised as satellite launches, have failed, said Reuters.
The latest test occurred in April with the rocket breaking up shortly after lift-off.
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Businessweek reported that the incident cost North Korea US food aid.
North Korea's newest threats were likely a response to the new US-South Korea agreement.
"We do not hide ... the strategic rocket forces are keeping within the scope of strike not only the bases of the puppet forces and the US. imperialist aggression forces' bases in the inviolable land of Korea but also Japan, Guam and the US. mainland," said an unidentified spokesman for North Korea's National Defence Commission, according to the Associated Press.
The US State Department refused to comment on the threat but said that the country was bound by UN resolutions to suspend its ballistic missile activity.
"Certainly rather than bragging about its missile capability, they ought to be feeding their own people," said State Department spokeswoman Victoria Nuland, according to Reuters.