Dec. 18 (Bloomberg) -- China??s President Hu Jintao said the country will play a more constructive role in global affairs, as the Communist government marked 30 years of free-market policies that transformed its economy into the world??s fourth-largest.

??We have overcome challenges in the past 30 years, from the breakup of the Soviet Union to facing down global sanctions, from the Asian financial crisis to the current global crisis,?? Hu said in a speech today to senior leaders at the Great Hall of the People in Beijing. ??Our international profile is rising and we will play an increasingly constructive role.??

The celebration of China??s economic connection with the world coincides with a slump in growth that presents a political challenge to a government whose legitimacy is tied to delivering greater prosperity. The $3.3 trillion economy is 68 times larger than in 1978, when former leader Deng Xiaoping began the reforms.

China??s shift to a capitalist system started when Deng approved an experiment that gave peasants the right to farm their own land. The changes initiated by the former revolutionary leader have supported growth averaging 9.9 percent for the past three decades. China overtook United Kingdom as the world??s fourth-largest economy, boosting average income.

In the last decade, China became a World Trade Organization member, transforming its economy into the world??s largest exporter of appliances, textile and consumer of raw materials. The nation hosted the Olympic Games in August, sent astronauts to space and is aiming to land a man on the moon by 2020.

The government will face a far tougher year in 2009 as the global recession deepens and a cooling domestic economy endangers social stability. Economic growth may slip to 5 percent or less, some economists forecast, before a 4 trillion yuan ($585 billion) stimulus package can revive expansion.

Tense Year Ahead

??The year to come is going to be quite tense,?? said Jean- Philippe B ja, senior researcher at the Paris-based Centre National de la Recherche Scientifique and the French Centre for Studies on Contemporary China in Hong Kong. ??If you base your legitimacy on delivering improvements in the economy and in living standards, then when you have an economic slowdown you have a problem.??

Imports and exports fell in November, inflation cooled and industrial production grew at the slowest rate since at least 1999. Home sales fel1 20.6 percent in the first 11 months while China??s benchmark stock index plunged 63 percent this year. Central bank Governor Zhou Xiaochuan said on Dec. 16 that he may add to the steepest interest-rate cuts in 11 years.

Unstoppable Expansion

A government exhibition this week in Beijing to mark the 30th anniversary chronicles what had seemed to be an unstoppable economic expansion of the world??s most populous nation.

A 25-meter wall of bar graphs on everything from rural income to currency reserves move in one direction: ever more steeply higher. A room of scale models displays Shanghai??s Pudong district bristling with uber-modern skyscrapers alongside the new development zone in eastern China??s Tianjin, where miniature Airbus SA planes circle a model port. Row after row of factories are blazoned with the names of international companies.

As the economic slowdown intensifies, the focus in China is shifting to laid-off workers as evidence points to rising social tensions and social instability.

Unemployment may reach 9.4 percent by year-end, the state- backed Chinese Academy of Social Sciences said in an annual report this week. The government??s target for urban registered unemployment is 4.5 percent for this year. Labor disputes are on the rise, with local governments in parts of eastern and southern China seeing a tripling of cases, according to the report.

Beja said 2009 will be ??a dangerous year?? because it marks key moments in a country with a long history, where anniversaries are significant. Next year will be the 20th anniversary of the 1989 Tiananmen Square crackdown on student demonstrators and the 10th year of a brutal campaign against the Falungong sect.

??In the recent history these have always been problematic for the leadership,?? Beja said.