That also constitutes a last guarantee for Iran, namely if the US dishonors its promise one day, Iran would still be able to resume its nuclear production. Thus Iran has benefited a lot from the agreement with the P5+1 countries.
However, the agreement is also good for US. Obama said his diplomacy "opened up a new path toward a world that is more secure", at least for the US.
After World War II, the US invested enormous manual and material resources in the Middle East; but its declining capabilities mean it is no longer possible for the US to shoulder as many global responsibilities as it used to. Solving its dispute with Iran can help the US avoid the danger of having to fight another war in the Middle East, which it cannot afford.
Besides, Iran has intimate relations with Syria and Afghanistan, so a better relationship with Iran means it will be easier to solve the problems in these two countries.
Improving the relationship with Iran will also aid the US' "rebalancing" in the Middle East. For decades, the US has had to rely on Israel and Saudi Arabia in the region; if Iran can be turned into a friend, the US would be able to prevent the Israeli or Saudi Arabian tail wagging the US dog and it would have strategic space in which to maneuver.
Further, solving the Iranian nuclear problem is part of the US' global strategy. Obama is concentrating on two main issues: promoting economic recovery at home; and shifting its strategic focus eastward abroad. Easing some of the pressure in the Middle East can help with both issues.
By shifting its strategic focus eastward the US means pivoting to East Asia, where there is another main opponent, the Democratic People's Republic of Korea. Thus it is predictable that US will refuse to follow a similar mode in interacting with DPRK - on the contrary, the US is likely to continue maintaining the tensions in East Asia, so that its troops have more reasons to continue staying in Japan and the Republic of Korea. That requires China take measures to maintain regional stability.
Hua Liming is China's former ambassador to Iran and the article is an excerpt of his interview with China Daily writer Zhang Zhouxiang.
(China Daily 01/20/2014 page9)