Foreign Minister Murray McCully has thanked US Secretary of State John Kerry for his "patient diplomacy" in achieving a nuclear agreement with Iran.
Mr McCully took a break from his United Nations (UN) duties to meet Mr Kerry in Washington.
The American diplomat thanked New Zealand for its support of the Iran deal at the UN.
"I am particularly grateful, as is [US] President [Barack] Obama, for New Zealand's very strong support of the agreement with Iran," says Mr Kerry. "We were privileged to have New Zealand as the presidency of the Security Council."
Mr McCully chaired the UN Security Council meeting, which endorsed the landmark deal between Iran and other nations last week.