US Secretary of State John Kerry is to make a statement in Saturday about progress in the Iran nuclear talks, a US official said.
Kerry would address journalists at 1430 GMT outside the Palais Coburg in Vienna where the negotiations have now stretched into their ninth day.
He would "deliver an update on the Iran negotiations," a senior State Department official said.
Global powers have been trying to hammer out a deal with Iran which would put a nuclear bomb out of Tehran's reach, and have set a fresh Tuesday deadline for an accord.
After an intense weekend of talks between Kerry and his Iranian counterpart Mohammad Javad Zarif, foreign ministers from other countries were due to return to Vienna Sunday.
Russia's top diplomat Sergei Lavrov was due back in the Austrian capital, the foreign ministry in Moscow said.
And the spokeswoman for the EU's Federica Mogherini sent a Twitter message saying the foreign policy chief would also make a statement in Vienna at 1545 GMT.
Meanwhile, French Foreign Minister Laurent Fabius, German counterpart Frank-Walter Steinmeier and Britain's Philip Hammond were also expected to rejoin the talks ahead of the final push towards Tuesday's deadline.
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