It was important that the Trump administration be "very strong" in enforcing the nuclear deal, Power told reporters on Friday.
"It's important that the communication continues," she added.
Trump, who will take office in a week, has threatened to either scrap the nuclear agreement or seek a better deal.
"We have succeeded in ensuring that Iran does not develop nuclear weapons ... it's working," Power further said, Reuters reported.
Iran and the Group 5+1 (Russia, China, the US, Britain, France, and Germany) reached the nuclear deal, known as the Joint Comprehensive Plan of Action, in July 2015 and implemented it in January last year.