Kim Yo-jong is said to have ambitions to succeed her brother as North Korea’s supreme leader (Picture: AP)

Kim Jong-un’s sister has warned North Korea is ready to take ‘quick, overwhelming action’ against the United States and South Korea after the two nations demonstrated a show of force against nuclear and missile threats.

Kim Yo-jong said officials were ‘keeping our eye on restless military moves’ and ‘could be forced to do something to cope with them’ – a day after the countries flew a nuclear-capable B-52 bomber in a joint military exercise.

The North has continued to fire test missiles this year after an unprecedented showcase of its arsenal in 2022.

The West has never shot them down, despite them being banned by the United Nations Security Council.

But Yo-jong cautioned that Pyongyang will see it as a ‘declaration of war’ if the US ever takes military action against the missiles.

The Pacific Ocean ‘does not belong to the dominium of the US or Japan’, she said, as reported by state media KCNA.

‘We keep our eye on the restless military moves by the U.S. forces and the South Korean puppet military and are always on standby to take appropriate, quick and overwhelming action at any time according to our judgment’, a statement read.

She said officials were ‘keeping our eye on restless military moves’ (Picture: Reuters)

‘The demonstrative military moves and all sorts of rhetoric by the US and South Korea, which go so extremely frantic as not to be overlooked, undoubtedly provide (North Korea) with conditions for being forced to do something to cope with them.’

It comes after Yo-jong previously threatened her country would use the Pacific ‘as our firing range’ if the US continued military drills.

Analysts say this would allow the isolated and nuclear-armed state to make technical advances, as well as signalling its military resolve.

In a separate statement, the chief of the Foreign News Section at North Korea’s Foreign Ministry has accused the US of ‘aggravating’ the situation by planning joint field exercises.

The US and South Korea have previously condemned North Korea’s  ‘grave provocation’.

They will conduct more than 10 days of large-scale military exercises known as the ‘Freedom Shield’ drills starting next week.

A Hwasong-15 intercontinental ballistic missile (ICBM) is launched at Pyongyang International Airport, in Pyongyang, North Korea (Picture: via Reuters)

It was claimed last week that Kim Jong-un’s wife and sister are quietly locked in a ‘power struggle’ to succeed the North Korean Supreme Leader.

The tyrant has ruled for 11 years now – and both his predecessors, his father and grandfather, ruled until they died.

Kim Yo Jong is said to want to succeed her brother as North Korea’s supreme leader.