Trump, appearing to recount a meeting with NATO leaders told a political rally in South Carolina on Saturday, "One of the presidents of a big country stood up, said: 'Well sir if we don't pay, and we're attacked by Russia - will you protect us?'

"I said: 'you didn't pay? You're delinquent?' He said: 'Yes, let's say that happened.' No I would not protect you, in fact I would encourage them to do whatever they want. You gotta pay."

White House spokesperson Andrew Bates, asked about Trump's comments, said, "Encouraging invasions of our closest allies by murderous regimes is appalling and unhinged - and it endangers American national security, global stability and our economy at home."

(Reporting by Mike Stone in Washington; Editing by Tom Hogue)