Former U.S. Ambassador to the United Nations John Negroponte said on Monday that the challenge posed by President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE for U.S. allies is figuring out how much of what he says he actually means.

"With President Trump, I think it always comes back to the question we've been asking ourselves right from the beginning when he was conducting his campaign, 'How much does he mean of what he says' or 'What part of what he says does he really mean?'" Negroponte told Hill.TV's Krystal Ball on "Rising."

Negroponte used Trump's recent comments about NATO as an example of how he often comes into summits with a disruptive attitude but leaves with a diplomatic message.

"He has this rather unique style. He's sort of the disrupter in chief, and he always goes in with this disruptive attitude, and then he tends to come out at the end with a more welcome message if you will. So the substance tends to be pretty good," he said.

"The form is sometimes a bit alarming, and so I think that's what happened in this particular instance, but I notice that when all was said and done, the United States signed this rather robust communique about NATO, and in his parting remarks, he said very positive things about NATO in his press conference and commended the importance of the institution and so forth."

Trump went into last week's NATO summit in Brussels with a confrontational attitude, demanding that allies increase their defense spending.

He said on last week before he left the summit that NATO allies agreed to “substantially up” their defense spending commitments.

Trump went on to praise the alliance in a tweet on Monday, calling the summit "truly great."

"Received many calls from leaders of NATO countries thanking me for helping to bring them together and to get them focused on financial obligations, both present & future. We had a truly great Summit that was inaccurately covered by much of the media. NATO is now strong & rich!" Trump said.