The statement follows another by North Korea on Tuesday which threw into doubt a six-country deal on giving up its nuclear arms, just one day after it was struck.

In that statement the North vowed to keep the weapons until Washington provides it with civilian atomic reactors.

In a commentary on Wednesday in its official communist party newspaper, Pyongyang said Washington is waiting for a chance to attack it.

"Clear is the ulterior intention of the U.S. talking about settlement of the nuclear issue through dialogue under the pretext of the six-party talks. In a word, it is to disarm the DPRK and stifle it with nuke," the paper said, according to a report carried on the official KCNA news agency.

DPRK is short for the North's official name, the Democratic People's Republic of Korea.

The commentary said the North "will steadily strengthen its war deterrent to defend national sovereignty and security with supreme vigilance".

The six countries agreed to a set of principles on Monday on winding up Pyongyang's nuclear programs in return for economic aid and recognizing its right to a civilian nuclear program.

The six agreed to discuss providing a light-water reactor "at an appropriate time". Washington pledged not to attack the North.

Washington has insisted that North Korea must completely, irreversibly and verifiably end its nuclear programs before consideration of a civilian nuclear program could begin.

North Korea has often said it was forced to develop nuclear weapons to counter what it saw as Washington's hostile policy toward it and has charged many times that Washington was going to attack it.

South Korean newspaper editorials on Wednesday charged North Korea with backsliding on the agreement to scrap its nuclear ambitions, saying Pyongyang has undermined trust and cast doubt on the deal by seeking civilian reactors up front.

"If the North continues to make unreasonable demands, even before the ink dries, no country will trust the North," the mainstream JoongAng Ilbo said in an editorial.

"This is a position destroying the roots of the joint statement issued only one day earlier (on Monday) at the six-country talks," it said.

South Korean government officials have said they will seek to mediate between Pyongyang and Washington, and believe Seoul can help them overcome their differences at the talks.

The United States, Japan and Russia told North Korea on Tuesday to stick to the six-country agreement to dismantle its nuclear weapons programs.

China has asked all sides to fulfil their promises.