A top Iranian official warned on Wednesday that Iran could withdraw from a key nuclear nonproliferation treaty if Europe followed through on its threats to reimpose sanctions on Tehran.

The remarks, from Iran’s deputy foreign minister, Kazem Gharibabadi, came during a rare on-the-record briefing with reporters in New York, where he was attending meetings at the United Nations. Mr. Gharibabadi laid out his country’s positions on a range of issues, setting the stage for nuclear talks with European counterparts in Istanbul on Friday.