WASHINGTON — The weather, and her reception here, were far colder than when she visited last summer during the Obama administration, but Federica Mogherini, the European Union’s foreign minister, made it clear that she can handle a chill in the air.

“I think we are entering into a different phase of our relationship,” Ms. Mogherini said Friday in a 30-minute interview, adding, “A more transactional approach means Europeans will be more transactional, and we will base our approach on our interests.”

But Ms. Mogherini said she had received important reassurances from top administration officials on the Iran nuclear deal and on Russian sanctions.

“I was reassured by what I heard in my meetings on the intention to stick to the full strict implementation of the agreement in all its parts,” Ms. Mogherini said of the Iran deal.