VIENNA: After Iran and major powers gave themselves until Monday to reach a nuclear agreement, US Secretary of State John Kerry warned that “difficult issues” remained in nuclear talks after meeting with his Iranian counterpart for 90 minutes on Saturday.

“Met with @FedericaMog and @JZarif this AM. Still have difficult issues to resolve,” Kerry said in a Tweet just minutes after ending his talks with EU foreign policy chief Federica Mogherini and his Iranian counterpart Mohammad Javad Zarif.

A senior Iran official also told AFP that there was “no time-limit” to the talks as negotiations hit the 15th day Saturday.

“We have no time-limit in order to reach a good deal,” the senior Iranian official said, asked if the negotiations could be formally extended again in a bid to end the current deadlock.

Before extending the talks to another third week, Tehran accused the West of throwing up new stumbling blocks to a deal. Both sides say there has been progress in two weeks of talks, but British Secretary Philip Hammond called it “painfully slow” and both he and his French counterpart, Laurent Fabius, left Vienna saying they would return on Saturday.

Having missed a Friday morning US congressional deadline, US and European Union officials said they were extending sanctions relief for Iran under an interim deal through Monday to provide more time for talks on a final deal.

Zarif said a deal was unlikely to be reached on Friday and negotiators would probably spend the weekend in Vienna. He sought to blame the West for the impasse.

“Now, they have excessive demands,” he said of the major powers’ negotiating position.

Britain’s Hammond said ministers would regroup on Saturday to see if they could overcome the remaining hurdles. “We are making progress, it’s painfully slow,” he told reporters before leaving Vienna.