Ardern said she would say in private to Biden what she had said publicly about her wish for the US to join the CPTPP rather than consider its Indo-Pacific Economic Framework an alternative.
There has been plenty of interest in Ardern in the U.S. because of the gun reforms in New Zealand after the 2019 mosque attacks.
Ardern's morning was spent in Washington DC meeting US Senators, including Republican Mitt Romney and Democrats Amy Klobuchar, Rick Larsen, Mark Warner and Jon Ossoff.
Ossoff is the youngest senator, aged 35, and has family links to New Zealand.
The Democrat Senator started his meeting with her by saying he strongly believed the US needed reforms, while Republican Mitt Romney said he supported the red flag proposals that had been adopted in some states.
However, they also pointed out that the situation in the US as being much different to New Zealand.
Ardern when asked by media if the US should change its gun reforms, she was cautious about making a statement about a different country's stance on such an issue.
"New Zealand had its own horrific experience and that we made changes as a result," she said - acknowledging the devastating March 15 mosque shootings in 2019.
Ardern said she had explained how the gun reforms in New Zealand had been able to happen after the horrific mosque attacks.
"Change is possible," she said.
She said a number of senators had raised her speech at Harvard University that she is due to give.
When asked if she would be making any changes to her speech, given the devastating deadly shooting at a Texas primary school, she acknowledged that was the case but would not exactly say what was in the speech.
In New York yesterday, she got high-powered backing in that call from Myron Brilliant, the executive vice president of the US Chamber of Commerce. After a meeting with Ardern, he said the US needed to "show up" in the Asia Pacific region, and should join the trade pact which Donald Trump had pulled the US out of in 2017.
"We should be part of a trade pact that the United States helped launch.
"She should definitely be pushing it - she should absolutely be encouraging the President of the United States to recognise what countries like New Zealand and Australia and Singapore and Japan are telling our President, which is that the United States needs to be in the region. Its presence needs to be there, not just as a counterweight to China but in terms of advancing our geopolitical strategic interests in the most dynamic and vibrant region in the world."
Ardern's day in New York wound up with an extended interview on the Late Show with Stephen Colbert on which Ardern ticked off her goal of promoting New Zealand as a tourist destination now the borders had reopened.
Ahead of her trip Ardern had said she would be "shameless" in taking the change to promote New Zealand – and she went to the extent of inviting Colbert to her wedding in an "invitation" written onto an advertisement for Air New Zealand's new direct flights between New York and Auckland.
That had started on a sombre note today after news of the tragic shooting at a school in Texas broke just before filming had started.
At least 18 children and three adults were killed in that shooting and Colbert, who has taken aim at US politicians for their failure to act on gun reform on his show in the past, began by asking Ardern about it after New Zealand's own experience with the Christchurch mosque attacks in 2019.
Ardern said New Zealand had gone through those attacks – "But when I watch from afar and see events such as this today, it's not as a politician. I see them just as a mother and I'm so sorry for what has happened here."
Ardern will travel to Boston after today's DC meetings where she will deliver the Commencement Address to Harvard University graduates – in the early hours of Friday morning NZ Time.
Ardern's handling of the Christchurch mosque attacks was one of the reasons Harvard University had given for inviting her to speak – she will be the first New Zealander to give the address.
