Trump's nuclear testing threat risks reigniting a global arms race, undermining decades of restraint among nuclear powers.

US president claims China, Russia have carried out secret nuclear weapon tests as he seeks to justify return to testing.

Trump defends U.S. nuclear testing resumption, citing weapons tests by Pakistan, China, and Russia as justification.

Trump's nuclear testing threat risks reigniting a global arms race, undermining decades of restraint among nuclear powers.

President Donald Trump's calls to ramp up nuclear weapons testing have put nuclear watchdogs on alert while experts say the United States has little to gain.