The world's eyes in recent weeks have been fixed on Iran. And, perhaps not so oddly, comparisons are being made between Iran today and China in 1989. Many have spoken about the possibility of a massacre occurring in Tehran, a sort of Tiananmen II; that looks unlikely now, although it is not clear what lies ahead. In fact, we don't really know what is going on in Iran because the government has banned the foreign media from seeing and reporting events. But, although Iran is a theocracy and China is run by atheists, there are striking similarities. In Iran, the president is, according to the constitution, not the most powerful official. He is the No 2, below the supreme leader. China, too, used to have a paramount leader while Deng Xiaoping was alive. Even though he did not hold the titles of state president, party general secretary or premier, he was in a position to anoint or destroy those who did hold those positions. Actually, in China, the president is not meant to be powerful: it is virtually a ceremonial post. The No 1 post is the general secretary of the Communist Party. However, since the tenure of Jiang Zemin , the offices of president and general secretary have been held by one individual. In Iran, the supreme leader's powers are defined in the constitution. And they are vast. They include not only laying down general policies for the country but also the power to appoint the head of the judiciary, as well as the head of the state radio and television administration. Current events in Iran also have relevance for Hong Kong, which is looking forward to being able to choose its chief executive by universal suffrage in 2017. Exactly how this will work has not been decided or, at least, has not been disclosed to Hongkongers. Many of those who will take part in the July 1 march tomorrow will, no doubt, demand genuine democracy rather than a system that will allow the authorities to set up a mechanism, known as a nominating committee, to sift out candidates not acceptable to Beijing, after which the electorate will be asked to choose between two or more pre-approved candidates. The Iranian presidential election shows that such a system is by no means foolproof. After all, each of the four candidates had been approved by the 12-member Guardian Council, which rejected all others. This process ensures that all candidates take similar positions on such vital issues as the country's nuclear development. And yet, despite this, the election still led to massive protests on the streets and violence that left more than a dozen people dead because of suspicions of fraud. Iran's Electoral Commission is supposed to wait three days before certifying the results of an election, to allow time for charges of irregularities to be dealt with. And yet, Supreme Leader Ayatollah Ali Khamenei endorsed the official announcement hours after the closing of the polls, when it appeared impossible for the millions of votes cast to already have been counted by hand. Hopefully, China will not back away from its promises about universal suffrage for the chief executive in 2017 and for the whole legislature in 2020. However, the widely publicised article by Liaison Office official Cao Erbao, asserting that there are two governing teams in Hong Kong - one consisting only of mainland officials - is very worrying. It certainly suggests that people should be on their guard against interference by the central government in Hong Kong's domestic affairs. In the end, whatever the future rules for universal suffrage may be, Beijing should be very careful to abide by them once they have been agreed. Hong Kong is not likely to experience the kind of nefarious activities that appear to have taken place in Iran, but no one should take anything for granted. Frank Ching is a Hong Kong-based writer and commentator.