German Foreign Minister Frank-Walter Steinmeier (L), French Foreign Minister Laurent Fabius (3rd L) and Chinese Foreign Minister Wang Yi (R) meet with foreign ministers from Russia, United States, the European Union, and Britain at a hotel in Vienna, Austria July 6, 2015.[Photo/Agencies]

VIENNA - Sides are working hard to resolve the six or seven remaining issues in the final Iranian nuclear talks, Chinese Foreign Minister Wang Yi on Tuesday told reporters in Vienna.

After holding meetings with foreign ministers of western countries and Iran, Wang is leaving Vienna but supposed to be back to the city for the final push of the comprehensive Iranian nuclear deal.

"All sides realize that this is the last negotiations," Wang said. "There are still around six or seven (remaining) issues," the Chinese Foreign Minister added.

Wang's remarks was echoed by the EU foreign policy chief Federica Mogherini who hinted the talks would not be extended to another round, saying the deadline of the talks could be treated in a flexible way to give the negotiators more time to finalize the deal.

"The time is now, it's a window that we are using at the maximum, but we are not closing the window and then opening another window at another time we are using the time now,"she said.

The most recent round of Iranian nuclear talks has missed its July 7 deadline, a week-long postponement of the original deadline, due to some tough unresolved issues, while the US said the new deadline could be extended till July 10.

"To allow for the additional time to negotiate, we are taking the necessary technical steps for the measures of the Joint Point of Action (the 2013 interim deal) to remain in place through July 10," US State Department spokeswoman Marie Harf said.

Iran and the five UN Security Council permanent members plus Germany have been negotiating over the past 16 moths to reach a long-term deal over Tehran's controversial atomic plan.

During the period, Iran would suspend some sensitive nuclear activities, in return, Western nations would partially relief some sanction imposed on Tehran.