President Donald Trump on Thursday vowed to begin testing US nuclear weapons “on an equal basis” with Russia and China, heralding a potentially major shift in decades of US policy at a time of growing tensions between the world’s nuclear-armed superpowers.

Beijing has been expanding its arsenal, and distrust between China and the United States over nuclear weapons has deepened, with little hope of an agreement.

The U.S. conducts several intercontinental ballistic missile test launches each year to maintain its nuclear deterrent.

Just days after touting a trade truce with China, President Trump acknowledged that China is "always watching us." American intelligence agencies say the Chinese have infiltrated parts of the U.S. power grid and water systems.