Tensions in the Korean peninsula have been running high for weeks, with signs the North may be preparing a long-range missile launch or a sixth nuclear test.
Washington has refused to rule out a military strike against the dictatorship in response to any attacks.
A spokesman for North Korea’s foreign ministry said Pyongyang was "fully ready to respond to any option taken by the US".
In a statement carried on the state-run KCNA news agency, a spokesman for the regime confirmed it will continue to bolster its "preemptive nuclear attack" capabilities unless Washington scrapped its “hostile” policies.
He added: "The DPRK's measures for bolstering the nuclear force to the maximum will be taken in a consecutive and successive way at any moment and any place decided by its supreme leadership,” apparently referring to a sixth nuclear test and using the North's official name, the Democratic Republic of Korea.
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North Korea has carried out five nuclear tests in the last 11 years and is widely believed to be making progress towards its dream of building a missile capable of delivering a warhead to the continental US.
Each Spring, the regime raises the tone of its warnings in response to joint exercises carried out by Washington and Seoul.
The regime has condemned these military exercises, accusing