Despite a global drop in nuclear arms, the Stockholm International Peace Research Institute (SIPRI) on Monday warned that countries are modernizing their arsenals, representing a worrying trend for arms control.

"At the start of 2020, the nine nuclear-armed states — the US, Russia, the UK, France, China, India, Pakistan, Israel and North Korea — together possessed an estimated 13,400 nuclear weapons," SIPRI said.

According to the report, that figure was down by 465 compared to 2019. The US and Russia, which possess 90% of the world's nuclear arms, were largely responsible for the decrease.

'New nuclear arms race'

Washington and Moscow are still adhering to the New START treaty that limits the number of deployed nuclear arms, although the accord is set to expire in February 2021. Neither country has committed to renewing it.

"In 2019, the forces of both countries remained below the limits specified by the treaty," the report said. However, they "have extensive and expensive programs underway to replace and modernize their nuclear warheads, missile and aircraft delivery systems, and nuclear weapon production facilities."

The New START treaty effectively extended Cold War-era arms controls on nuclear arms between the two countries. But researchers warned that an end to the arms control agreement could herald a new era.

"The loss of key channels of communication between Russia and the USA … could potentially lead to a new nuclear arms race," said Shannon Kile, director of SIPRI's nuclear arms control program.

Read more: US boosted nuclear arms budget by billions, report says

Modernizing arsenals

China, the third-largest holder of nuclear arms behind the US and Russia, isn't part of the treaty, which observers believe is a central motivating factor behind Washington's unwillingness to recommit to the accord.

The SIPRI report said that China has taken significant steps to modernize its arsenal, including expanding its capabilities in classic military domains.

"China is in the middle of a significant modernization of its nuclear arsenal," said SIPRI researchers. "It is developing a so-called nuclear triad for the first time, made up of new land- and sea-based missiles and nuclear-capable aircraft."

Experts believe the US is holding out in order to bring China into a new agreement limiting deployed nuclear arms. However, China has suggested it would not join talks to reduce its strategic weapons.

Other nuclear powers in the process of modernizing their arsenals include France and the UK.

ls/stb (Reuters, EFE)

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