Relations between Washington and the hermit state have continued to decrease in recent weeks, as US troops joined forces with South Korea for military training drills.
And numerous Chinese subs have been seen in the Korean peninsula, while the North appears to be accelerating and advancing its submarine-launched ballistic missile programme.
Tensions between the US and North Korea continued this week
Now experts have warned the US nuclear warning system remains heightened, as nuclear analysts continue to keep a close eye on Kim Jong-Un.
The DefCon Warning System is a private intelligence organisation which has monitored and assessed nuclear threats against the United States by national entities for more than 33 years.
North Korea have threatened to break UN rules and launch another missile test
Over the past few months, the warning accelerated to level three following increased tensions between US and Russia, with insiders fearing the West was creeping closer to nuclear war.
Level three means US troops could be mobilised in as little as 15 minutes.
While level four, which was implemented on April 17 and has the exercise term “double take”, is described as having increased intelligence watch and strengthened security measures.
Kim Jong-Un warned North Korea was on the "brink of war"
The DEFCON warning comes as tensions continue to escalate
And it appears experts are now far more preoccupied with the prospect of nuclear war with North Korea than Russia.
Officials said in a statement: “Due to continuing tensions in Korea and the volatility of the situation, we are continuing to hold at Blue for the time being.
“We will continue to reassess and adjust the code as necessary.
“We caution the public to not mistake a lack of headlines in the news as a lowering of hostilities.”
Explosive images as South and North Korea test their deadly power
Tue, May 2, 2017
South Korea and US military held the integrated live fire exercise amid tensions over nuclear issues in the Korean Peninsula
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South Korean K1A2 tanks fires live rounds
Due to continuing tensions in Korea and the volatility of the situation, we are continuing to hold at Blue for the time being.
DefCon Warning System
The statement added the public should make their own evaluations and not rely on the DefCon Warning System for strategic planning.
And citizens are urged to learn what steps to take in the event of a nuclear attack.
The DefCon Warning System team also warn it is not just North Korea causing international tensions.
China has warned leaders to stay calm surrounding heightened tensions
They said: “Continuing in the area, military activity between Japan and China near disputed islands increases while China launches its second aircraft carrier.
“Japan continues to reassess its non-combat policy and is beginning to take a more proactive stance with regard to both North Korea and China.
“The United States says Iran fulfilling terms of nuclear deal, but later says that Iran is not meeting ‘spirit’ of agreement.
“Pakistan military doctrine currently includes uses of nuclear weapons if the country believes it would not result in massive retaliation from India, a significantly dangerous theory.
“Russia continues to fly bombers near Alaska while NATO deploys troops to Poland and the United States calls for faster deployment of space-warfare weaponry.”