Secretary of State Antony Blinken has sought to take pressure off the US by saying that it will become “very hard” to return to the 2015 Iran nuclear agreement if negotiations in Vienna continue without progress.

Washington its dragging its feet on removing sanctions despite having declared that it is ready to undo the wrongs of the former Trump administration which abandoned the Joint Comprehensive Plan of Action (JCPOA) in 2018.

Speaking to reporters in Paris on Friday, Blinken said Washington still has “serious differences” with Tehran despite months of diplomatic efforts in the Austrian capital to resurrect the nuclear agreement.

Iran is insisting that while it is against attritive negotiations, it is ready to wait as long as it takes before the US remove all sanctions imposed, reimposed and relabeled by the former government in a verifiable manner.

“There will come a point, yes, where it will be very hard to return back to the standards set by the [deal],” Blinken said. “We haven’t reached that point – I can’t put a date on it – but it’s something that we’re conscious of.”

If Iran “continues to spin ever more sophisticated centrifuges” and steps up uranium enrichment, it will bring nearer the “breakout” time, he added.