Nuclear negotiations between the United States and Iran are expected to continue in Switzerland on March 27.
U.S. Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif met for a first round of discussions in Lausanne on Lake Geneva on March 26.
The talks come with a self-imposed March 31 deadline looming to reach a framework deal.
Six world powers and Iran have been negotiating for two years to reach a deal to limit Iran's nuclear program in exchange for sanctions relief.
In particular, Washington and its partners want Iran to cut the number of centrifuges it uses to enrich uranium, material that can be used in warheads.
Iran denies it is secretly developing a nuclear weapon as the West suspects.
U.S. officials say the March 31 deadline is achievable but remains uncertain.
The Iranian side was more upbeat.
Ali Akbar Salehi, Tehran's top nuclear official, said the talks have already reached a "common understanding" on technical issues.