One of the world’s most famous scholars said he was "frightened" by Donald Trump’s tweet on "strengthening and expanding" nuclear capabilities in the US.
Noam Chomsky, professor emeritus at the Massachusetts Institute of Technology, said Mr Trump’s tweet was "one of the most frightening things I’ve seen recently".
"Putin’s is bad enough," Mr Chomsky told the Huffington Post, "but at least it has a defensive cast. It’s about Russia’s borders, not Mexico’s."
Russian president Vladimir Putin also said he wanted to build his nuclear capabilities.
"We need to strengthen the military potential of strategic nuclear forces, especially with missile complexes that can reliably penetrate any existing and prospective missile defense systems," Mr Putin said, according to Agence France-Presse.
"We must carefully monitor any changes in the balance of power and in the political-military situation in the world, especially along Russian borders, and quickly adapt plans for neutralizing threats to our country."
Mr Chomsky said the statements from the world leaders could bring about a change to the Bulletin of the Atomic Scientists’ Doomsday Clock, which is an internationally recognised symbol of how close we are to destroying humanity with our own technology - and is due to be updated in 2017. He said the clock might move from three minutes to midnight to "even closer to midnight".
The professor has been a vocal critic of the president-elect, comparing his campaign pledges and rhetoric to Nazi Germany.
But Mr Chomsky was not the only opposing voice on Mr Trump's views on nuclear weapons, given the president-elect’s history of dubious statements on the subject.
Mr Trump has previously suggested that South Korea and Japan should obtain their own nuclear weapons, and he has even reportedly asked a foreign policy adviser why the US has nuclear weapons if it does not use them. Mr Trump denied asking the question.
The US owns around 4,600 nuclear warheads and, along with Russia, owns the vast majority of nuclear weapons in the world.
Mr Trump’s tweet, limited to 140 characters, did not give national security experts and advisers much reassurance for anything other than his preference for heated rhetoric.
John Noonan, a Republican national security expert who advised presidential candidates Jeb Bush and Mitt Romney, wrote on twitter: “But imagine having to turn launch keys not knowing if we were under attack or it if was b/c foreign leaders said a mean thing on twitter.”
Mr Trump has done little to assure his critics that he has the presence of mind and the steadiness to make a quick decision regarding an imminent nuclear threat.
If a missile was launched from Russia, it would take 30 minutes to hit the White House - and just 12 minutes from the Atlantic Ocean.
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