Iran said on Wednesday it will resume full compliance with a 2015 nuclear deal if it can sell its oil or get a $15 billion credit line guaranteed by future crude sales.

Deputy Foreign Minister Abbas Araghchi expressed doubt, however, that such a plan could be agreed before a looming deadline set by Iran to further scale back its commitments ­under the nuclear accord.

The agreement - known formally as the Joint Comprehensive Plan of Action (JCPOA) - has been crumbling since the US unilaterally withdrew from it in May last year.

France has been trying to convince the US to offer Iran some sort of relief from sanctions it has reimposed on the Islamic republic since its pullout.

"Iran ... will return to full implementation of the JCPOA only if it is able to sell its oil and to fully benefit from the income from these sales," said Araghchi.

Araghchi, speaking days ­after leading an economic delegation to France, ruled out any renegotiation of the JCPOA, but said Iran was open to talks on how to implement it better.

"Returning to full implementation of the JCPOA is subject to receiving $15 billion over a period of four months, otherwise the process of Iran reducing its commitments will continue," he said.

But Araghchi cast doubt on the likelihood of an agreement being reached before the deadline set by Iran.

"I don't think the European countries will be able to take an effective step before Friday ... so we will take the third step," he said.

Iran has hit back with countermeasures in response to the US withdrawal from the JCPOA, which gave it relief from sanctions in return for curbs on its nuclear program.

In July, it said it had increased its stockpile of enriched uranium to beyond the maximum set by the deal. It later  announced it had exceeded a cap on the level of enrichment of its stocks.