US intelligence agencies believe that China is developing a new generation of nuclear weapons and has conducted at least one covert explosive test in recent years as part of a broader push to completely transform its nuclear arsenal into the world's most technologically advanced, according to multiple sources familiar with the US intelligence assessments.

The US has said that China must be included in a future arms deal. The 15-year agreement restraining the US and Russia's nuclear arsenals is no more, opening the door for distrust that could raise the risk of miscalculation, arms control experts say.