U.S. Secretary of State John Kerry said on Sunday major differences persist between the Iranian regime and six world powers negotiating on Tehran's nuclear program.
British Foreign Secretary William Hague said on Sunday it was crucial for the Iranian regime "to be more realistic about what is necessary" to reach a nuclear deal with six major powers that would end sanctions against the regime in exchange for curbs on its atomic work.
The Iranian regime's Deputy Foreign Minister Abbas Araqchi delivered a similar message. He was quoted by the regime's Arabic language al-Alam television as saying that "disputes over all major and important issues still remain. We have not been able to narrow the gaps on major issues and it is not clear whether we can do it."
"It is vital to make certain that Iran is not going to develop a nuclear weapon and that their programme is peaceful and that's what we're here to try and achieve and I hope we can make some progress," Kerry said in Vienna.
German Foreign Minister Frank-Walter Steinmeier told reporters that Germany and the other members of the six-power group have tried to persuade Iran of the urgency of a deal.
"This may be the last chance for a long time to peacefully resolve the dispute over Iran's nuclear programme," he told reporters. "It's now up to Iran to decide whether it wants cooperation with the international community or to remain in isolation. ... The ball is in Iran's court."
Failure to seal a deal would mean the limited sanctions relief currently in place for the Iranian regime would end and Tehran could expect tougher sanctions, above all from the United States.