North Korea could have 40 nuclear warheads by 2020, according to a Swedish Institute focused on nuclear disarmament, Chosun Media reports.

“This is a rough estimate, I would emphasize, and it’s based on what we know about North Korea’s fizzle material production capabilities relevant for nuclear weapons,” Shannon Kile, the director of nuclear disarmament, arms control and non-proliferation program for the Stockholm International Peace Research Institute, said during a press conference held in Seoul, South Korea, on Monday.

SIPRI said the median estimate was based on open sources from satellites and experts around the world.

The outfit last year speculated that North Korea had 20 to 30 nuclear warheads.

North Korea on Monday said it would not consider abandoning its nuclear weapons unless external threats are fully removed. Negotiations for a peace deal between Pyongyang and the United States have stalled since a February summit between North Korean leader Kim Jong Un and President Donald Trump in Vietnam collapsed over disagreements over sanctions relief in exchange for disarmament measures.

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