Iran's Foreign Minister Javad Zarif has warned that Tehran would further cut its commitments under a 2015 nuclear deal unless European states acted to save the pact by Thursday, but that this did not mean the "end of talks", Iranian news agencies reported.
Zarif said late on Tuesday that President Hassan Rouhani would soon announce details of the cuts. Implementation of this step does not mean the end of talks," he added.
France has proposed offering Iran about $15bn in credit lines until year-end if Tehran comes fully back into compliance with the deal.
French Foreign Minister Jean-Yves Le Drian said talks on the credit arrangement, which would be guaranteed by Iranian oil revenues, were continuing, but approval from the United States would be crucial.
The idea is "to exchange a credit line guaranteed by oil in return for, one, a return to the JCPOA (Iran nuclear deal) ... and two, security in the Gulf and the opening of negotiations on regional security and a post-2025 (nuclear programme)," Le Drian told reporters.
"All this (pre)supposes that President Trump issues waivers."
Le Drian added that there was still "lots to work out" and that negotiations were "still very fragile".
A senior Iranian official later confrimed that Tehran would return to its commitments under the deal only if it got $15bn for oil sales over four months, the the semi-official Fars news agency said on Wednesday.
"Our return to the full implementation of the nuclear accord is subject to the receipt of $15bn over a four-month period, otherwise the process of reducing Iran's commitments will continue," Fars quoted Deputy Foreign Minister Abbas Araqchi as saying.
But Araqchi said there were still "serious disagreements on the agenda" of any future talks between Iran and its nuclear deal partners. But Araqchi said there were still "serious disagreements on the agenda" of any future talks between Iran and its nuclear deal partners.
European leaders have struggled to dampen brewing confrontation between Tehran and Washington since US President Donald Trump pulled out of the deal, which assures Iran access to world trade in return for curbs on its nuclear programme.
The US withdrew from the deal in 2018 and reimposed sanctions on oil - steps that signatories to the deal strongly opposed.
In response Iran reduced some of the limits on nuclear material in the deal, and has set another deadline for Thursday to further downgrade its commitment.
For the US to permit a credit line for Iran would contradict its stated policy of imposing "maximum pressure", to force Tehran to rein in its nuclear and missile programmes as well as what Washington views as its destabilising regional behaviour.
A US State Department spokeswoman referred Reuters' queries about France's proposal to the White House, which did not immediately respond to a request for comment.
But in another sign of more US pressure against Iran, the US Treasury imposed sanctions on Tuesday against Iranian space agencies.