In a complete reversal, Trump advocates the United States enter a nuclear arms race, despite having an arsenal that could destroy human civilization many times over.

With less than a month until his inauguration, Trump dropped a tweet (or what passes for a "press release" for his incoming administration) calling for the United States to "greatly strengthen and expand" its nuclear capabilities.

Russian president Vladimir Putin led off the ratcheted-up rhetoric during an annual end-of-year meeting with his top military advisors.

He spoke hours after President Vladimir Putin said Russian Federation needs to bolster its military nuclear potential.

Putin directly referenced the U.S. as a motivation for building on Russia's weapons, saying that America is "actively modernizing its nuclear air bombs and keeping them in Europe...."

Trump's tweet, below, comes hours after Putin delivered a speech to his Defense Ministry Board advocating an upgrade of his country's weapons systems.

USA ballistic missile submarines, bombers, and land-based missiles - the nuclear triad - are expected to reach the end of their useful lives over the next decade. "Why do we make them?" In the weeks leading up to the election, Donald Trump stated he would not take the use of nuclear weapons off the table.

Donald Trump said, "it's only a question of time". "And unfortunately, we have a nuclear world now".

United States nuclear capabilities are already enormous.

During his campaign, the former Apprentice host expressed interest in using nuclear weapons, asking during an interview with MSNBC in March, "Somebody hits us within ISIS, you wouldn't fight back with a nuke?"

Trump could also be referring to plans to modernize the current U.S. nuclear arsenal that are now underway and will cost hundreds of billions of dollars.

The president-elect's transition website says he "recognizes the uniquely catastrophic threats posed by nuclear weapons and cyberattacks", adding that he will modernize the nuclear arsenal "to ensure it continues to be an effective deterrent". "We are old. We're exhausted. A very bad thing".

The U.S. now possesses approximately 7,100 nuclear weapons, according to the nonpartisan Arms Control Association. And even if Trump's tweet referred to sustaining and modernizing this arsenal, at a cost of over $1 trillion over the next 30 years, Reif believes that's still "unsustainable".