Elon Musk, a close adviser to President-elect Donald J. Trump, met with Iran’s ambassador to the United Nations on Monday in New York in a session that two Iranian officials described as a discussion of how to defuse tensions between Iran and the United States.

The Iranians said the meeting between Mr. Musk and Ambassador Amir Saeid Iravani lasted more than an hour and was held at a secret location. The Iranians, who spoke on the condition of anonymity because they were not authorized to discuss policy publicly, described the meeting as “positive” and “good news.”