North Korea has warned Donald Trump that it is prepared for war and is ready to use its "powerful nuclear deterrent".

Vice foreign minister Han Song Ryol blamed the US pre sident for building up a "vicious cycle" of tensions on the Korean Peninsula, saying that his "aggressive" tweets were "making trouble".

In an exclusive interview with The Associated Press in Pyongyang, Mr Han warned the US against provoking North Korea militarily, saying: "We will go to war if they choose."

He said: "If the US comes with reckless military manoeuvres then we will confront it with the DPRK's pre-emptive strike," referring to North Korea by its official name, the Democratic People's Republic of Korea.

"We've got a powerful nuclear deterrent already in our hands, and we certainly will not keep our arms crossed in the face of a US pre-emptive strike."

Speaking through an interpreter provided by the foreign ministry, Mr Han was calm and polite but forceful throughout the 40-minute interview.

Tensions are deepening as the US has sent an aircraft carrier to waters off the peninsula and is conducting its biggest-ever joint military exercises with South Korea.

Pyongyang, meanwhile, recently launched a ballistic missile and some experts say it could conduct another nuclear test at virtually any time.

"That is something that our headquarters decides," Mr Han said of what would be North Korea's sixth nuclear test.

"At a time and at a place where the headquarters deems necessary, it will take place."

Many North Korea watchers believe North Korea could have a viable nuclear warhead and a ballistic missile capable of hitting the US mainland on Mr Trump's watch as president - within the next few years.

Mr Han, however, said North Korea blames Mr Trump and the US for the rising tensions.

He cited not only the US-South Korean wargames and the deployment of the aircraft carrier, the USS Carl Vinson, but also a tweet Mr Trump posted on Tuesday in which he said the North is "looking for trouble".

The president also tweeted that if China does not do its part to rein in Pyongyang's nuclear ambitions, the US can handle it.

"Trump is always making provocations with his aggressive words," Mr Han said. "So that's why. It's not the DPRK but the US and Trump that makes trouble."

The annual military exercises have consistently infuriated the North, which views them as rehearsals for an invasion.

Washington and Seoul deny that, but reports that exercises have included "decapitation strikes" aimed at the North's leadership have fanned Pyongyang's anger.

"As long as the nuclear threats and blackmail go on with the military exercises, we will carry forward with our national defence build-up, the core of which is the nuclear arms build-up," Mr Han said.

"Whatever comes from the US, we will cope with it. We are fully prepared to handle it."

Outwardly, there are few signs of concern in North Korea despite the rising tensions.

Instead, the country is gearing up for its biggest holiday of the year, the 105th anniversary of the birth of the late Kim Il Sung, the country's founder and leader Kim Jong Un's grandfather.

The Saturday anniversary may provide the world with a look at some of North Korea's arsenal.

Expectations are high the North may put its newest missiles on display during a military parade that could be held to mark the event.

AP

South Korea's Foreign Ministry criticised Mr Han's remarks saying they reveal the "true colours of North Korea's government that is bellicose and a breaker of regulations".

It said North Korea will face strong punishment it will find hard to withstand if it makes a significant provocation, such as another nuclear test or an intercontinental ballistic missile launch.

The ministry says South Korea is in close discussions with others including China, North Korea's only major ally, on ways to respond should the North take such actions.

AP