Vienna: Iran and the P5+1 group of world powers aimed to finish the latest round of nuclear talks "in the timeframe" that all parties have set out, said US Secretary of State John Kerry in Vienna.
"That's our goal," Kerry said on Sunday, two days ahead of the July 7 deadline, while adding that the US would "put every bit of pressure possible on it to try to do so".
After meeting with his Iranian counterpart Mohammad Javad Zarif on Sunday afternoon, Kerry told reporters that "it is now time to see whether or not we are able to close an agreement", with his foreign minister colleagues returning back to Vienna.
However, despite genuine progress made in the past few days, Kerry said: "We are not yet where we need to be on several of the most difficult issues."
Kerry also told reporters that while he completely agrees with Zarif that Iran and world powers "have never been closer" to a deal, the negotiation could go either way at this point.
"We want a good agreement. Only a good agreement. We are not gonna shave anywhere at the margins just to get an agreement," Kerry said, adding that "we're not there yet, I emphasise that."
Meanwhile, European Union foreign policy chief Federica Mogherini also said on Thursday: "We're moving forward, but we're not there yet."
Zarif said on Friday in a video on YouTube that despite some remaining differences, Iran and its counterparts "have never been closer to a lasting outcome".
China remains optimistic. Chinese Foreign Minister Wang Yi said on Thursday that a comprehensive Iranian nuclear deal is very likely to be reached after intensive meetings between Iran and six world powers.
"The possibility of reaching a deal is very high, and a deal should be agreed," Wang told reporters.
Despite the optimism, gaps remain in some areas of the talks, especially on the pace and timing of sanction relief.
Earlier, reports said that Iran may change tack on the Lausanne framework, raising concern of a possible setback in the talks.
Iran and five UN Security Council permanent members plus Germany (P5+1) missed the previously set self-imposed June 30 deadline for a comprehensive deal. Both sides agreed to extend the deadline to July 7.
All parties have been negotiating over the past 16 months to reach a long-term deal over Tehran's disputed atomic plan.
In a successful deal, Iran would suspend some sensitive nuclear activities, and in return, Western states would partially relieve some sanctions imposed on Tehran.