Iran and six major world powers are continuing negotiations in Vienna, past a previously set deadline, on a long-term nuclear agreement as they tackle the most contentious issues.
Chinese Foreign Minister Wang Yi says all sides are working hard to resolve the remaining six or seven issues.
"The most important progress is that, under the push of the foreign ministers' meetings, both sides of the negotiation have put forward a package of thoughts and plans concerning the remaining issues. This paves the way for final negotiation on substantive issues including the wording of the deal."
European Union's foreign policy chief Federica Mogherini, who is chairing the talks, has hinted the negotiations will not be extended to another round.
"We are continuing to negotiate for the next couple of days. This does not mean we are extending our deadline. I told you, one week ago more or less, we are interpreting in a flexible way our deadline, which means that we are taking the time, the days we still need, to finalize the agreement, which is something that is still possible even if now we are getting into the difficult time."
The comprehensive deal under discussion is aimed at curbing Tehran's most sensitive nuclear work for a decade or more, in exchange for relief from economic sanctions.
The negotiators had initially given themselves an extra week when they missed a June 30 deadline for a final agreement, but a push in recent days has not been enough to hammer out the deal.
Major sticking points are said to include the duration of limits on Iran's nuclear research and development, guidelines for international inspections and how sanctions will be lifted.
Tehran is also demanding that the UN ban on the import and export of conventional arms and ballistic missiles be lifted as part of any deal.
The United States had wanted an agreement finalized by Wednesday at the latest so that it could be submitted to Congress for approval by Thursday.
If a deal is presented later, the congressional review period will double from 30 days to 60.
