Story highlights Review could lead to more than $1 trillion in spending over nearly 30 years

A review of ballistic missile defenses also is underway

(CNN) The Pentagon is putting the finishing touches on the first comprehensive review of US nuclear forces in nearly eight years. It's shaping up as President Donald Trump's signature nuclear weapons initiative in the face of a growing North Korean nuclear threat.

The review, which may allow Trump to put his mark on the nuclear inventory for decades to come, could lead to more than $1 trillion in spending over nearly 30 years.

There have been three such reviews since the end of the Cold War, the most recent in 2010 under President Barack Obama.

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"This Nuclear Posture Review is unique in that it is the first one to occur after a notable negative evolution in the security environment," one defense official said. "Threats have become more stark and volatile since 2010, and a fresh look at nuclear posture is essential to countering these threats."

Trump ordered the review in a presidential memorandum last January 27, a week after he took office. The memo called for a Pentagon review "to ensure that the United States nuclear deterrent is modern, robust, flexible, resilient, ready, and appropriately tailored to deter 21st-century threats and reassure our allies."

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