Nuclear powers are continuing to modernize their arsenals despite an overall decrease in the number of nuclear warheads, a Sweden-based peace research institute said Monday.

Nine nuclear-weapon powers — the United States, Russia, the United Kingdom, France, China, India, Pakistan, Israel and North Korea — had an estimated 13,865 nuclear weapons at the start of 2019, the Stockholm International Peace Research Institute (SIPRI) reported. Deployed warheads and those held in reserve or awaiting dismantlement are included in the estimate.

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The number is down by around 600 nuclear weapons from the previous year, driven mainly by Russia and the United States reducing their arsenals under the New START nuclear arms reduction treaty. Russia and the United States have 6,500 and 6,185 nuclear warheads respectively, about a quarter of which are deployed.

There are no talks planned between Moscow and Washington to extend New START once it expires in 2021.

"The prospects for a continuing negotiated reduction of Russian and US nuclear forces appears increasingly unlikely given the political and military differences between the two countries," said Shannon Kile, SIPRI's director of nuclear disarmament, arms control and non-proliferation program.

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Modernization programs

SIPRI highlighted a trend of Russia and the United States pursuing extensive and expensive programs to replace and modernize their nuclear arsenals, missiles and delivery systems.

"In 2018, the US Department of Defense set out plans to develop new nuclear weapons and modify others to give them expanded military roles and missions," SIPRI said in its briefing. "The nuclear arsenals of the other nuclear-armed states are considerably smaller, but all are either developing or deploying new weapon systems or have announced their intention to do so."

Nuclear rivals India and Pakistan, which have 130 to 140 and 150 to 160 nuclear warheads respectively, are increasing the size of their arsenals while also developing new systems.

"India and Pakistan are expanding their military fissile material production capabilities on a scale that may lead to significant increases in the size of their nuclear weapon inventories over the next decade," said Kile.

North Korea has an estimated 20 to 30 nuclear warheads, which SIPRI said was a priority for the country's national security strategy. However, it noted that North Korea has not tested a nuclear weapon or long-range ballistic missile since it entered into denuclearization talks with the United States in 2018.

France has 300 nuclear warheads, China 290, the UK 200 and Israel 80 to 90.

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