Iran nuclear talks to resume in Vienna
The remaining partners to the 2015 accord have been engaged in negotiations since early April to try to revive it.
The third round of talks started on Tuesday and, after several days of technical discussions between expert groups and delegations, will resume on Saturday.
The service of EU foreign policy chief Josep Borrell said in a statement that delegates from Britain, China, France, Germany, Iran and Russia would meet in person at around 3 pm (1300 GMT).
"Participants will continue their discussions in view of a possible return of the United States to the JCPOA and on how to ensure the full and effective implementation of the JCPOA," the statement said, using the acronym of the agreement's formal name.
A European diplomat said that the American, European, Russian and Chinese delegations held a joint meeting on Saturday morning, but without Iranian representation as Tehran has refused to negotiate with the US directly.
After almost a month of talks, the parties this week expressed a desire to "speed up" the negotiations.