Negotiators from the latest round of talks on Iran's nuclear issues say a couple of more days may be needed for reaching a final deal.
The P5+1 group and Iran met in Vienna over the weekend to strike a long-term deal before the June 30th deadline.
Vice minister of foreign affairs Li Baodong is heading the Chinese delegation to the talks.
He says it is possible to make a comprehensive deal on the nuclear issue within a week, though many tough issues still need to be resolved.
"We noticed that much progress has been made on many fronts, no doubt that still number of very tough issues remain to be addressed, but we hope that we can cut a deal on time."
The statement came as Iran's Foreign Minister Mohammed Javad Zarif set to fly back to Tehran from Vienna, in order to consult with the country's leadership on the state of negotiations.
A framework agreement was reached in Switzerland on April 2nd.
Coordinating the meetings, European Union foreign policy chief, Federica Mogherini says the final deal will be drafted within days.
"So we have tasked our negotiating teams to continue work immediately tonight on the text and to try and close all the issues of the translation of the political understanding that we found in Lausanne into text that is solid enough for the coming days."
Iran and five UN Security Council permanent members plus Germany have been negotiating over the past 14 months to reach a long-term deal over Tehran's disputed atomic plan.
During the period, Iran would suspend some sensitive nuclear activates; in return, western states would partially relieve sanctions imposed on Tehran.