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