US Secretary of State John Kerry and his Iranian counterpart, Foreign Minister Mohammad Javad Zarif, met Sunday on the sidelines of the Munich Security Conference, the State Department said.

Kerry and Zarif “discussed the upcoming negotiations with the P5+1 and the EU on a comprehensive agreement that will begin in Vienna next month,” a senior US State Department official said.

Nuclear talks between the P5+1 states and Iran are set to reconvene on February 18.

“Kerry reiterated the importance of both sides negotiating in good faith and Iran abiding by its commitments under the Joint Plan of Action (agreed in November),” said the official.

“He also made clear that the United States will continue to enforce existing sanctions,” he added.

The official said Kerry also pressed Zarif to “work cooperatively with us” to help detained US citizens Robert Levinson, Amir Hekmati and Saeed Abedini return home.

State Department spokesperson Jen Psaki tweeted the news of the meeting.

Further details of the meeting were not immediately available.

The US and Iran have not had formal diplomatic relations since 1980, after Iranians stormed the US Embassy in Tehran and took 52 hostage for over a year.