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US authorities confirmed the test was successful and the B61-12 gravity bomb is expected to go into production within three years.

The B61-12 gravity bombs were 'inert' but they were dropped from F-15E fighter jets at Tonopah Test Range in Nevada on August 8, the National Nuclear Security Administration said.

The tests were intended to check the bomb’s “non-nuclear functions and the aircraft’s capability to deliver the weapon.”

Despite the weapons' nuclear capability being disabled the message to Kim Jong-un's North Korea could not be clearer.

A statement from the NNSA said: “B61-12 gravity bombs, without a nuclear warhead, were dropped from F-15E fighter jets at Tonopah Test Range in Nevada on August 8. The tests were intended to check the bomb's 'non-nuclear functions and the aircraft's capability to deliver the weapon.”