The pause went on until someone commented on it.
Other leaders had made their "not good" views clear at the very start of his speech which included a lengthy diatribe about the evils of the globalism the UN was based on.
He began with a boast that his two-year old administration "has accomplished more than that almost any administration in the history of our country".
The leaders' response was a multilateral one: they laughed.
It was enough to stop Trump in his tracks: "I didn't expect that reaction but that's okay."
It was that laugh that led the bulletins from then on.
Ardern did not even allow herself that indulgence. She sat completely dead-pan at that moment and as Trump set out plans to restrict foreign aid to countries which were "friends" of the US, criticised the UN, and other countries for not putting enough funding into it.
"We reject the ideology of globalism and we embrace the doctrine of sovereignty," he said.
He said every country should be able to pursue its own unique version of sovereignty.
"The US will not tell you how to live, or work or worship. We only ask you honour our sovereignty in return."
In the next breath, he criticised Germany's energy policy, saying it was on track to become totally dependent on Russian oil. "Not good."
A photo of Germany's delegation taken at that moment showed delegates either laughing or with a look of disbelief.
Ardern remained a sphinx. Even Christiane Amanpour hadn't been able to drag any direct comments about Trump out of her during a 12-minute interview on CNN.
Ardern will deliver her own statement to the General Assembly tomorrow morning NZ time.
Anyone who has any inkling about Ardern's politics will know where she stands - and it is not with Trump. She did after all take to the streets after his election in a Woman's March.
Ardern has already sided with the likes of "like-minded" European leaders, such as French President Emmanuel Macron, on most of the issues.
When Macron presented his statement, he hit back at Trump's eschewing of multilateralism. Ardern has said she will cover the same topic.
But Ardern no longer has the luxury of being able to voice it in blunt terms.
In her one brief encounter with Trump, she managed to get in a nice word about Trump's efforts with North Korea and a reminder that New Zealand was still waiting, and hoping, and wishing and praying for an exemption from US tariffs on steel and aluminium.
Then her partner Clarke Gayford knocked over a flag during a photo op with Trump and wife Melania. They all smiled and said cheese for a photo which was yet to be released at deadline.
Or perhaps Ardern just saw it for the mid-term election campaign bluster some of it was - after all, Trump was on his home turf and America is never more first than during an election campaign.
COMING UP:
Prime Minister Jacinda Ardern faces one of the highlights of her visit to New York with an appearance on The Late Show with Stephen Colbert this morning (NZ Time).
It is her final US media engagement of her time in New York, following a slot on NBC's Today show and an interview on CNN with Christiane Amanpour, looking at the reaction to Ardern's baby Neve.
Colbert got in some practice in understanding the New Zealand accent by getting Flight of the Conchords stars Bret McKenzie and Jemaine Clement on the show two days ahead of Ardern.
It comes after Ardern met with Hollywood actress Anne Hathaway, star of movies including The Devil wears Prada and The Princess Diaries yesterday.
Hathaway had requested the meeting with Ardern - the actress takes an interest in issues such as paid parental leave.
Ardern said she was familiar with Hathaway's work and pleased she had recognised the work New Zealand had done for children and families.
It is one of Ardern's busiest days in New York, including a meeting with Canada's Prime Minister Justin Trudeau and Chile's President Sebastian Pinera last night, speaking at a business forum and French President Emmanuel Macron's Global Planet Summit and ending with The Late Show.
