"The Administration’s current plans for US nuclear forces would cost $494 billion over the 2019–2028 period — $94 billion more than CBO’s 2017 estimate for the 2017–2026 period, in part because modernization programs continue to ramp up," the estimate said.
Aside from more costly modernization programs, the rise in cost is also due to inflation, new weapons and new command-and-control systems, the document said.
Trump's administration has recently presented their military ambitions in the Missile Defense Review, in which the US claims that it depends on nuclear deterrence to address Russian and Chinese intercontinental ballistic missile capabilities. In particular, the document stresses more complex offensive missile threats to the homeland, such as hypersonic glide vehicles (HGV) and advanced cruise missiles are on the horizon.
The review suggests that improving the US ability to track these emerging risks could make defending against cruise missile and HGV threats possible.
In general, the new Missile Defense Review depicts a strategy that will set the path to strengthen the United States' current defence capabilities and make the case for urgent investment into new ones.