“I am sorry to say that I am less confident today than 28 hours before...about the prospects of closing the deal right now,” Borrell, the High Representative of the EU for Foreign Affairs and Security Policy, told reporters in Brussels this week.

Currently, Iran and the United States are indirectly negotiating – via the mediation of the European Union – a return to the so-called nuclear deal, which could ultimately lead to the lifting of the U.S. sanctions on Iran’s oil industry and exports. Former U.S. President Donald Trump withdrew the United States from the Joint Comprehensive Plan of Action (JCPOA) in 2018 and re-imposed sanctions on Iran’s oil exports that had been lifted in the wake of the original deal in 2015.

At the end of last week, Iran sent its written response to what could be a final draft of a possible deal, although it didn’t reveal what the response was.

“The sent text has a constructive approach with the aim of finalizing the negotiations,” Nasser Kanaani, spokesman for the Iranian Foreign Ministry, said in a statement carried by the Associated Press.

The U.S. confirmed it had received the Iranian response via EU mediators, but dismissed the Iranian suggestions as “not constructive”.

“We are studying it and will respond through the EU, but unfortunately it is not constructive,” the U.S. Department of the State said. The U.S. didn’t reveal details of the response, either.

“Based on their answer, we appear to be moving backwards,” a senior official at the Biden Administration told POLITICO on Thursday evening.

A deal, which now looks farther than it did a week ago, would eventually allow the return of around 1 million barrels per day (bpd) of Iranian oil on the global market at some point next year.