Mr Trump tweeted the stark message from his personal Twitter account at 4.50pm today in a very unseasonal message.
He said: The United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes."
The tweet has been retweeted thousands of times.
What do you think to his claim?
Mr Trump is set to take office in 2017 after beating Hillary Clinton to the top job.
More to follow.