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Russia has declassified the first image of its new thermonuclear-armed intercontinental ballistic missile.

The RS-28 Sarmat could carry a payload capable of wiping out a landmass "the size of Texas or France," according to a report by the Kremlin-aligned Sputnik news agency.

An image of an RS-28 Sarmat missile. Makeyev Rocket Design Bureau

Known colloquially as "Satan 2," the missile will replace the RS-36M — which was dubbed "Satan" by NATO after entering service in the 1970s.

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Robert Kelley, a former nuclear weapons expert at the U.S. Department of Energy, said the new missile was likely an upgrade of electronics — rather than explosive power or range.

"The range of the missiles will be about the same, the explosive destructive power will be about the same [but] the reliability, flexibility and confidence [in the warheads' ability to hit their targets] will go way up," said Kelley, who is now a now a distinguished associate fellow at the Stockholm International Peace Research Institute.

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He added: "Your iPhone can do thousands of more things today than in the 1970s when these systems were first deployed. Many of the clunky electronic circuits of that era no longer exist and no one knows how to make them anymore."

According to Russian media, the missile's first stage engine PDU-99 was tested in August, while a hypersonic warhead was reportedly tested in April.

The new version of the Sarmat is expected to enter service late next year.