By John Irish and Arshad Mohammed
PARIS (Reuters) - Serious differences persist between the United States and Iran over how they might resume compliance with the 2015 Iran nuclear deal despite making some progress in their latest indirect talks in Vienna, a senior U.S. official said on Wednesday.
The talks were likely to require several rounds, their outcome remained uncertain and they were not near conclusion, the senior U.S. State Department official told reporters in a conference call.
The main differences are over what sanctions the United States will need to remove and what steps Iran will need to take to resume its obligations to curb its nuclear program, said the official, who spoke on condition of anonymity.
"There still are disagreements and, in some cases, pretty important ones," he said. "We are not near the conclusion of these negotiations. The outcome is still uncertain. We have made some progress."
Earlier, the European parties to the Iran nuclear deal said they had seen progress in the first two rounds of indirect U.S.-Iran talks but there were still major hurdles.