Risk-averse in the best of times, China's Communist Party leadership is expected to use its biggest meeting of the year for an even tighter show of political unity in the face of the global economic crisis and public calls for political change.

Delegates to the National People's Congress session that starts Thursday are being told to cool even their usually tepid debates. Lots of talk about getting the economy back on track is expected. Strong measures are not.

"If the meetings are dull, then the party is firmly in control. If they are eventful, then their control might be seen as slipping," Oxford University China expert Steve Tsang said.

The National People's Congress has traditionally served as a rubber stamp for policies determined by the party. The 2,000-plus delegates include influential leaders from the ministries, the provinces and the military.

Now the economic crisis is straining China's unwritten social contract, under which the public agrees to one-party rule in exchange for rising living standards. As millions of workers lose their jobs and the export-heavy economy stumbles, the country's leaders are closing ranks even further, squelching dissent and holding the line on political reform.

Growth fell to 6.8 percent in the fourth quarter, sluggish by Chinese standards, while unemployment is at nearly 10 percent, according to some government economists.

Labor disputes nearly doubled last year due to factory shutdowns, and some 26 million workers from the countryside have lost their jobs in the more urban, developed parts of China, raising fears of rural unrest. In anticipation of more trouble, the government last week said police chiefs from the country's 3,000-plus counties will be trained to handle protests and other threats to social order.

Delegates to the national session, which runs through March 13, may discuss expanding a 4 trillion yuan ($586 billion) stimulus plan that was announced last fall.

But Chinese leaders "don't want any surprises. They want to project an image of unity from the top level all the way down to the base," said Ding Xueliang, a former Communist Party official who now teaches at the Hong Kong University of Science and Technology.

"With all these pressing issues, it's not at all the time to confront political reform," he said.

The economic challenges come amid renewed calls for political change.

One open letter issued last month by civil rights and rural activists demands an end to rigged elections for village chiefs, and the extension of educational and social security benefits that urban Chinese enjoy to rural families as well. Titled the "Eight Suggestions for Rural Reform," it claims to have gathered 11,000 signatures.

The boldest call for reform, known as "Charter '08," began circulating on the Internet in December and won endorsements from hundreds of intellectuals and pro-democracy activists both inside China and overseas. It declares authoritarianism is on the wane and calls for a new Chinese constitution, separation of powers, competitive elections and other hallmarks of Western democracy.

"We're hoping for more freedom and transparency, but is that the way the government is heading?" said Mao Yushi, a respected 80-year-old economist who runs a private think tank in Beijing and has often been outspoken on the need for political reform.

Dozens of signers, not including Mao, have been questioned by authorities, and a co-author of the charter remains in police detention. One signer, Tang Xiaozhao, who works for a nonprofit agency in Shanghai, wrote on her blog that police told her the charter "was against the party and against socialism."

Other factors contribute to the political chill. This year brings a series of sensitive dates, including two Tibetan uprisings this month and the 20th anniversary in June of the Tiananmen Square crackdown on democracy activists.

Cheng Li, a China politics expert at the Brookings Institution in Washington, said he sees demand for action growing strident over the next decade as the single-party system proves increasingly inadequate to the needs of a rapidly changing society.

"The leaders realize that. They're just not ready to move on it yet," Li said.