US Secretary of State Rex Tillerson has said nuclear weapons will not bring security for North Korea's government, amid an escalating war of words between officials from the two countries.
It's a notable addition to the meeting since the European Union had invited foreign ministers who were party to the deal.
That the president gave the nod to Haley and not Tillerson - the secretary of state who outranks her as a member of the Cabinet - was not necessarily evidence, in and of itself, that she was upstaging him.
This will be the highest-level known encounter between the Trump administration's national security team and Iranian officials so far. Haley is also being vetted by Democrats as a possible White House contender. This wasn't a favor to her, mind you, it was a favor to then-South Carolina lieutenant governor Henry McMaster, who endorsed Trump (and who coveted Haley's job for his own).
In Trump's speech Tuesday, he denounced North Korea, vowing to "totally destroy" the country if the USA was provoked. And it was Haley who introduced Trump at the UN's opening session on internal reforms, touting his "businessman's eye" for seeing potential in the world body that Trump had criticized as ineffectual during his campaign.
"So he is being tested with the sanctions, voices from every corner of the world".
U.S. Ambassador to the United Nations.
"The mentally deranged behavior of the US president openly expressing on the United Nations arena the unethical will to "totally destroy" a sovereign state, beyond the boundary of threats of regime change or overturn of social system, makes even those with normal thinking think about discretion and composure", the North Korean leader said.
In a surprising twist during a presidency filled with surprises, Haley has become the face of American diplomacy in the age of Trump.
Tillerson, by contrast, has found himself on the losing side of key internal policy arguments, most notably over the fate of the Iran nuclear deal and the Paris climate accord.
"Our new executive order will cut off sources of revenue that fund North Korea's efforts to develop the deadliest weapons known to humankind", Trump said.
Haley's fierce denunciation of what she calls systemic bias against Israel at the United Nations has made her the darling of Israeli hawks and raised her star with pro-Israel American Republicans. "And I think they're going to have to think carefully about their responsibilities in this regard".