International Atomic Energy Agency (IAEA) Director General Rafael Grossi meets with head of Iran's Atomic Energy Organization Mohammad Eslami, in Tehran, Iran, September 12, 2021.  (Photo: REUTERS)

Washington was prepared to be patient, the US official told reporters, but said at some point Iran's nuclear advances would overtake the deal and the United States and its partners would have to decide whether Iran was willing to revive it.

The senior US State Department official said in a telephone briefing that the US still wants to come back to the table and the window of opportunity is open but it won't be open forever if Iran takes a different course.

Tehran signaled on Tuesday that negotiations would resume in a few weeks without giving a specific date.

Under the 2015 deal, Iran curbed its uranium enrichment program in return for the lifting of economic sanctions. Then-US President Donald Trump quit the deal in 2018 and re-imposed harsh sanctions on Iran, prompting Tehran to take steps to violate its nuclear limits.