The US is set to go to the brink of war with its ally North Korea if it continues to threaten to launch nuclear missiles.US President Donald Trump is expected to declare a national emergency over North Korea on Monday as a response to the country’s nuclear and missile programs, but analysts say the US is unlikely to go beyond the initial declarations made by the Obama administration, and the war could drag on for years.

According to Reuters, US Defense Secretary Jim Mattis is expected on Monday to declare that the US will attack North Korea “if necessary, as a last resort” if the country continues to defy US sanctions.

The US is not likely to go the full distance and it could take several years to bring the war to a close, analysts said.

However, the war would be a significant blow to US foreign policy and would likely lead to a major increase in tensions with North Korean leader Kim Jong-un.

According the BBC, “the US and its allies would face a much larger challenge to deterring Pyongyang from developing nuclear weapons, and it is unclear how long they could afford to wait before an attack”.

If North Korea continued to threaten nuclear attacks, the US would likely take military action to protect itself, while North Korea could “use its nuclear weapons and ballistic missiles to threaten the US mainland,” analysts said in a report published on Monday by the US Strategic Command.

North Korea is believed to be in the process of building a nuclear-tipped missile capable of striking the US, as well as its main nuclear arsenal.

North Korean leader Ri Yong-ho has repeatedly threatened to attack the US with a nuclear warhead, and has said that he has the ability to strike the US from anywhere in the world.

Analysts say it is possible the war in North Korea will continue for decades, with North Koreans likely to try to develop a missile that can reach the US.

The war could also be an “imminent threat”, if North Korea does not stop its nuclear and ballistic missile programs.

If the war escalates, analysts say it would also lead to an increase in global instability.