It could take years and hundreds of millions of dollars for the US to restart nuclear testing.

The Washington Post on October 31 quoted experts as saying that the US restarting nuclear testing would take years and cost hundreds of millions of dollars. The Nevada test site, where the US last conducted a nuclear explosion more than three decades ago, now relies mainly on computer simulations instead of actual explosions.

The news comes after President Donald Trump announced this week that he had "instructed the War Department to begin testing our Nuclear Weapons on an equal basis [with Russia and China]" and said that preparations would begin immediately.

It was not immediately clear whether Mr Trump was referring to underground nuclear explosions. None of the three countries (the US, Russia, China) have conducted similar tests in decades. Moscow, for its part, has warned that any US nuclear explosion would result in a proportionate response.

The Washington Post pointed out that if Washington were to move forward with the plan, the responsibility would not fall to the Pentagon but to the Department of Energy, specifically the National Nuclear Security Administration (NNSA), which oversees the Nevada Test Site.

Experts say resuming testing at the site would come at a high cost. Ernest Moniz, who headed the Department of Energy under former President Barack Obama, estimated that even a “showy” explosion conducted without collecting scientific data would take “probably a year” to prepare.

Corey Hinderstein, a former senior NNSA official, said the agency would need to dig a new vertical tunnel at an estimated cost of about $100 million.

Another major hurdle is the lack of real-world experience. Paul Dickman, a longtime nuclear official, warned that the US may have trouble finding people with direct testing experience. He said that competent test directors “are not desk-bound bureaucrats or PowerPoint-reading nerds” but “people with extensive field experience.”

For years, Washington has relied on computer simulations and so-called “subcritical” tests – experiments stopped just short of a nuclear explosion – to maintain confidence in its arsenal. The last of more than 1,000 tests conducted by the US took place in 1992.

Mr Trump’s announcement coincided with Russian President Vladimir Putin announcing the successful tests of two advanced nuclear systems: the Burevestnik cruise missile with unlimited range and the Poseidon underwater drone, both of which are said to use groundbreaking compact nuclear reactors as propulsion.