Last-ditch talks are still underway in Switzerland ahead of Tuesday's deadline for a preliminary deal on Iran's nuclear program.
Foreign ministers from the five permanent members of the UN Security Council, plus Germany, have been meeting with their Iranian counterpart in the hopes of working out a breakthrough after almost 18 months of negotiations.
Chinese Foreign Minister Wang Yi says all sides have made clear exactly what the sticking points are and how they see these obstacles be overcome.
He says they remain optimistic about a potential solution.
For his part, Iranian Deputy Foreign Minister Abbas Araghchi says they're still working through various proposals.
"We are still not in the position to be able to say we are close to resolving the remaining issues, but we are hopeful and we'll continue the efforts."
Iran and the P5+1 have been working to try to break an impasse in negotiations aimed at ensuring that Tehran cannot develop a nuclear bomb.
In exchange, the UN sanctions being imposed on Iran will be lifted.
At issue are which sanctions will be lifted, and how much work Iran will be able to do when it comes to further nuclear development.
If a preliminary deal can be completed Tuesday, the technical details of a final deal have to be done by the end of June.
