Under President-elect Donald Trump America will invite a nuclear arms race Trump said on Friday, clarifying a tweet about the US expanding its nuclear weapons arsenal.

"Let it be an arms race, we will outmatch them at every pass," Trump told MSNBC Morning Joe host Mika Brzezinski on 23 December.

Trump's Press Secretary Sean Spicer appeared on the morning news talk show. "He just left but he was on the phone with the president-elect," Morning Joe host Joe Scarborough said. "Mika asked the president-elect, while we had the opportunity, what his position was on trying to clarify the tweet yesterday regarding the nuclear arsenal."

Trump, Scarborough said, told her that America would "outlast" every other country in a nuclear arms race.

On 22 December, Trump tweeted the "United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes." Throughout his campaign, Trump spoke about increasing Americas nuclear arsenal.

Responding to Trump's tweet at an hours-long press conference in Moscow, Russia, on 23 December, President Vladimir Putin shrugged off Trump's tweet as "nothing new."

"During his election campaign, he said the US needed to bolster nuclear capabilities and armed forces in general, and there is nothing new," Putin said. On 22 December, before Trump's tweet Putin had said that Russia is strong enough to take on an aggressive adversary.

"I said that we are improving our nuclear capabilities, and that Russia is stronger [than] any potential aggressor," he said. "It [is] very important, I used that word, aggressor. I did not use it accidentally. Who is an aggressor? An aggressor is someone who can potentially attack Russia. So we are stronger than any potential aggressor."

Massachusetts Institute of Technology professor and intellectual Noam Chomsky told the Huffington Post that Trump's tweet is, "one of the most frightening statements I've seen recently."

"Putin's is bad enough," Chomsky said, "but at least it has a defensive cast. It's about Russia's borders."