Despite the progress, there are still disagreements. The number of centrifuges that Iran can have is the most important issue in which the parties differ. Iran has approximately 19,000 centrifuges, and 10,000 of them are in operation. Iran claimed it wants 50,000 centrifuges while the West insisted that Iran can only have thousands. The French foreign minister proposed Iran can only have hundreds, which is obviously not realistic.

According to the latest speech by Khamenei, it seems that the West will accept 10,000, although it's not confirmed.

The second issue is the duration of the agreement. Iran argued the agreement should be a confidence building measure that lasts five years. After that, Iran should have the legal rights enjoyed by other NPT signatories. The West insisted that the agreement should be effective for two decades.

The third issue is whether the parties can agree on the time period for the removal of sanctions on Iran. Though Iran is aware the sanctions can only be removed gradually, it argues that sanctions should be removed as soon as possible.

These are the major sticking points, yet other issues are also on the table. For instance, the West intended to include Iran's missile program in the negotiation, but Iran refused to talk about that because it has nothing to do with Iran's nuclear program. Iran also refused to talk about the closure of Fordo enrichment facilities saying the West has illegitimately claimed it is not accessible to military attack.

Barack Obama regards the breakthrough of the nuclear deadlock and reconciliation of U.S.-Iran relations as his potential presidential legacy. The U.S. realizes that it cannot move forward with its Middle East policy without the support of Iran. The recent challenges of ISIL have enhanced such a belief.

Hassan Rouhani, a moderate cleric, also regards defrosting Iran's relations with the U.S. as an inevitable path that Iran will have to choose. Without normal relations with the U.S., Iran can neither achieve its development goals or carrying out its regional roles.

Two scenarios will be highly likely. The first is both governments, the U.S. and Iran, demonstrate sufficient courage to make concessions at the last moment. That should be good news for the two countries and the world.

The second is the parties agree to extend the negotiation another six months or for an undetermined period of time. The interim agreement froze the status of the issue, which should be a sound foundation for a potential negotiation.

The author is a columnist with China.org.cn. For more information please visit: http://china.org.cn/opinion/jinliangxiang.htm

Opinion articles reflect the views of their authors, not necessarily those of China.org.cn.