"China is pursuing a 'nuclear triad' with the development of a nuclear-capable air-launched ballistic missile (ALBM) and improving its ground and sea-based nuclear capabilities", the report said.
The report, an annual assessment submitted to Congress, also said Beijing is moving its strategic nuclear arsenal to a more rapid launch footing.
"New developments in 2019 further suggest that China intends to increase the peacetime readiness of its nuclear forces by moving to a launch-on-warning (LOW) posture with an expanded silo-based force", the report read.
China is expanding its inventory of the multi-role DF-26, a mobile, ground-launched intermediate-range ballistic missile system capable of rapidly swapping conventional and nuclear warheads, the Defence Department added.