Parties involved in the Iran nuclear deal have agreed to discuss the lifting of US sanctions and ways to limit Tehran's nuclear program as a way to revive the accord.
US and Iranian delegates held separate meetings with officials from the European Union and others who served as intermediaries in the talks that began in Vienna on Tuesday.
This is the first full-scale effort to restart talks between the two countries since Washington pulled out of the accord in 2018 and re-imposed sanctions.
After the US withdrawal, Iran accelerated uranium enrichment activities in breach of the accord.
US President Joe Biden wants to rejoin the accord.
Iran's Deputy Foreign Minister Abbas Araqchi said after the talks that they were constructive and heading in the right direction.
He also said the next meeting is likely to be held on Friday.
White House spokesperson Jen Psaki suggested that the negotiations will be a difficult and long process. She said the administration continues to believe that diplomatic path is the right way forward that benefits both sides.