To me, the most touching moment of President Bush’s recent trip to Asia was his final stopover in Mongolia.

Fifteen years ago, the descendants of Genghis Khan drove the communist leadership from power. Within months, free elections were held, and a free Mongolia was born. Mongolia has made the transition from communism to freedom and established a vibrant democracy and opened up the economy. Mr. Bush rightly told his courageous hosts: “You’re an example of success for this region and for the world.”

Listening to Mr. Bush pay tribute to Mongolians’ contributions to freedom’s cause, I can’t help thinking: If Mongolia, with 800 years of history and once part of China, can have democracy, then I don’t see any legitimate reason why my hometown Hong Kong, after 150 years as a British colony and now under China’s control, has to wait any longer. If 2.8 million Mongolians, many of them farmers and semi-nomadic herders, can be trusted to choose their leader, then 6.8 million Hong Kong people, many of them middle-class and accustomed to British rule of law, surely should be mature enough to decide their own fate.

For those who insist economic development must precede political openness, just compare the gross domestic product per capita of Mongolia and that of Hong Kong: $1,900 vs. $34,200 (even higher than that of its former colonial sovereignty Britain’s $29,600). And Hong Kong isn’t ready for democracy?

Of course it is. To his credit, even China-appointed Hong Kong chief executive Donald Tsang, seems to agree. Speaking in Washington last month, Mr. Tsang declared “There is no doubt that Hong Kong people are worldly-wise and sophisticated enough to elect their own political leaders. But … the development of our political system is not up to me alone.

“Hong Kong cannot act unilaterally in this regard, although some people naively believe we can and should. They have forgotten that Hong Kong is part of China. Our political development is as much a national issue as it is an issue for Hong Kong,” Mr. Tsang confessed.

The answer lies in the painful truth that China, despite getting stronger and wealthier every day, remains deeply hostile to democracy, whether in Hong Kong or in the mainland. Political reform, portrayed by some almost as a natural outcome of economic liberalization, remains nowhere to be found in China.

From Bill Clinton to George W. Bush, the U.S. has been participating in the biggest gamble of our era, betting heavily on economic forces would finally crack China. In a few decades, China may indeed become an open society, as many free traders and panda huggers are predicting, or it may become a more threatening dictatorship, as how I view the current trend is headed. Won’t it be great if we could find a crystal ball that would tell us the answer now? In a way, we do have a crystal ball in Hong Kong.

We don’t have to wait 30 years to have an idea how China would look then. Try to picture China as a gigantic Hong Kong. As China’s current GDP per capita of $5,600 rises, the country will look more and more like Hong Kong, with a sizable middle class and thus an irresistible thrive for self-determination as the theory goes. The Chinese people would be much more affluent and their lives would improve in nearly every sense. However, there’s no guarantee that political freedom and democracy would appear automatically. This is exactly Hong Kong’s predicament today.

When China took over Hong Kong from Britain in 1997, Hong Kong people were promised that the “ultimate aim” is to elect the chief executive and the whole legislature by “universal suffrage.” A 10-year transition of “gradual and orderly progress” was then implemented with the expectation of realizing the ultimate aim as early as 2007. However, China gets cold feet and is blocking any meaningful forward move. The struggle in Hong Kong, to cut the long story short, is simply asking China to honor its own promises. Nothing more and nothing less.

One may be tempted to think that Hong Kong is too tiny to make any difference in shaping the future of China: 6.8 million people are only a drop in the vast ocean of 1.3 billion people. When China becomes democratic, Hong Kong would be just fine. Be patient. It may be true but I beg to differ. The formula should be the other way around. Unless Hong Kong, the only enclave of freedom in China, survives, I don’t see much hope in China ever getting democratic.

On Tuesday, when Secretary of State Rice receives Martin Lee, the Hong Kong democracy veteran who is heading a small delegation to seek Washington’s help this week, she should bear this in mind. Help Mr. Lee and his colleagues defend Hong Kong’s endangered freedom today, and the chance of turning China into a responsible stakeholder tomorrow would be so much enhanced. If Hong Kong is lost, then forget about the rest of China. And that’s why Hong Kong is so important.

Mr. Liu is a Washington-based columnist of Hong Kong’s Apple Daily.