Diplomats laughed at Donald Trump because they "loved his honesty", according to US ambassador to the United Nations Nikki Haley.
But one diplomat said he was laughing at the "far-fetched, unreasonable, or insane" speech the US President gave on Tuesday (local time).
"In less than two years, my administration has accomplished more than almost any administration in the history of our country - it's so true," the former reality TV star said, to guffaws from the usually staid audience at the UN General Assembly.
"I didn't expect that reaction but that's okay," Mr Trump responded.
Appearing on one of the President's favourite TV shows Fox & Friends on Wednesday (local time), Ms Haley defended her boss' choice of words.
"When he said that, they loved how honest he is. It's not diplomatic and they find it funny. When he goes and he is very truthful, they kind of were taken back by it.
"All day yesterday, they were falling over themselves to get a picture with him, to talk about how great his speech was... They love that he's honest with them and they've never seen anything like it, so there's respect there."
Mr Trump contradicted himself, telling reporters at a rare press conference the line was "meant to get some laughter".
"They weren't laughing at me, they were laughing with me. We had fun," he said.
"Sometimes, when we see a behaviour or listen to arguments or notions that seem so far-fetched, unreasonable, or insane, there is almost natural reaction of laughing," a Latin American representative said on the condition of anonymity.
"It is not laughing at a good joke, but a nervous laugh, or a bad joke turned laughable precisely because the guy who tells the joke doesn't realise how bad it is."
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Another said what would "resonate well at a political rally in America sounded a little awkward at the UN".
"He doesn't have any concept of diplomacy," an Asian diplomat said, but admitting his bellicose style appeared to be working on North Korea.