An unarmed Trident II D5 missile launches from the Ohio-class ballistic missile submarine USS Nebraska (SSBN 739) off the coast of California. Photo: IC

US President Donald Trump's "usable" low-yield nuclear weapons could cause misjudgments and put the world at risk of a nuclear war, experts warned Wednesday as the US began production of such nukes.

Ordered by Trump in the Nuclear Posture Review in 2018, production of the W76-2 warhead has started at the Pantax Plant in Texas, according to a statement from the US National Nuclear Security Agency, US media outlet Defense News reported on Tuesday.

Designed to be smaller than the nuclear bombs dropped on Hiroshima, Japan during the World War II, the low-yield nukes are based on the US Navy's submarine-launched ballistic missile Trident. The first batch is scheduled for delivery by the end of September, the report said.

The Trump administration said the low-yield nukes would give the US a more flexible deterrent, because its enemy might think the US would not use its current nukes as they are "too big to use" and would cause untold civilian casualties, the Guardian reported.

With these more "usable" warheads, the US is loosening nuclear weapons constraints, the Guardian said.

For a long time, nuclear weapons were only meant as strategic deterrence to gain political and diplomatic leverage and maintain peace, but Song Zhongping, a military expert and TV commentator, told the Global Times on Wednesday that US low-yield nuclear weapons might result in the actual use of nukes on battlefields. 

Unlike high-yield strategic nukes that target large political, economical and military hubs, the low-yield bombs are intended for tactical strikes on targets like smaller military bases, experts said.

However, such a deployment might cause serious misjudgment.

Upon detecting a missile launch, the receiving end does not know whether the missile carries high-yield or low-yield warhead, and is likely to react as if a larger warhead has been launched, Defense News reported, quoting nonproliferation advocates and Democrats in the US Congress.

China's principle is to never use nuclear weapons first, but Song said nuclear powers including China and Russia have a nuclear retaliation mechanism that will launch counterattacks with nukes, but that mechanism probably does not distinguish between a tactical nuclear attack and a strategic one.

While the US might use a low-yield nuke used in a conventional warfare to limit damage, it could escalate into a full-scale nuclear warfare resulting in a worldwide disaster, according to Song.

China is surrounded by nuclear powers, and if a low-yield nuke is used, more countries will want to use it, posing serious challenges to China, Song said.

Five nuclear powers - the US, China, France, Russia and the UK - are holding a conference in Beijing from Wednesday to Thursday. They are responsible for safeguarding global peace, security and stability, Geng Shuang, Chinese Foreign Ministry spokesperson said on Wednesday. They should recognize the serious challenges facing global security, Geng said.