The US on Wednesday morning test-launched an intercontinental ballistic missile to show the readiness of the country's nuclear foces.
The test launched at 1.13am local time from Vandenberg Space Force Base in California, the base said on Twitter.
Describing the test as "routine", the Pentagon on Tuesday said it was scheduled far in advance and that Russia and other countries were notified.
“There will be an operational test launch of an Air Force Global Strike command unarmed Minuteman III intercontinental ballistic missile early tomorrow morning, September 7, from Vandenberg Space Force Base in California,” Pentagon spokesman Pat Ryder said on Tuesday.
The purpose of Wednesday's test was "to demonstrate the readiness of US nuclear forces”, Mr Ryder said.
The US successfully carried out a test launch of a Minuteman III missile on August 16 after it was delayed several times because of escalating tensions over Ukraine and Taiwan.
The missile carried a test re-entry vehicle, which in a conflict could be armed with a nuclear warhead.
The re-entry vehicle travelled about 6,760 kilometres to the Kwajalein Atoll in the Marshall Islands in the western Pacific.
Mr Ryder said the two tests were scheduled long ago and occurred close together because of the first test's postponement.
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Agence France-Presse contributed to this report
