China's new leadership holds a key meeting this weekend that state media are trumpeting as a likely "watershed" for economic reform, but analysts caution details of its decisions are likely to be vague and implementation gradual.

The four-day session of the full 376-strong Communist Party Central Committee begins Saturday at a closely guarded private hotel in Beijing.

Known as the Third Plenum, it traditionally sets the economic tone for a government's five-year term.

In the past, such meetings have been used to signal far-reaching changes in how China does business, and state-run media say that anticipation has been building.

The official Xinhua news agency proclaimed that the plenum "is expected to be a watershed as drastic economic policies will be unveiled".

Other reports have singled out land reform as a key issue, while a government think-tank called for dismantling the residency registration system known as hukou, which restricts access to medical insurance and other benefits for migrants.

But analysts are largely unconvinced and say broad brushstrokes rather than firm details are likely to emerge from the meeting.

Cai Hongbin, a professor at Peking University's Guanghua School of Management, said key issues such as urbanisation, the social safety net, taxation and financial reforms would be discussed.

"But I don't see a sweeping policy package with many specific major policy changes basically across the spectrum," Cai told reporters, emphasising more time was needed given the complexity of the issues.

Precise measures were more likely to be included in China's 13th five-year plan, to be announced in 2015, he said.

'Reforms more complex than in the past'

China most notably signalled major changes at a Third Plenum in 1978, when it embarked on the landmark reform drive that has seen it transformed over the past 35 years from a Communist-style command economy into a key driver of global growth, trade and investment.

But the impetus for far-reaching change this time is seen by some as nowhere near so compelling.

"Historically, China has implemented ground-breaking reforms when the economy has faced some serious challenges," Nomura International economists in Hong Kong wrote in a report.

"However, we believe that pressures are not yet sufficient to demand such rapid implementation, while the reforms are more complex than they have been in the past."

Although the economy is no longer completely party- and state-controlled, the ruling body holds huge sway, with officials in charge of key elements, such as the exchange rate, that in other countries are left mostly to markets. State-owned enterprises also play a key role.

The plenum comes a year after China began a once-a-decade leadership change, with Xi Jinping taking over as party general secretary in November and state president in March.

Calling corruption the biggest threat to continued party rule, Xi quickly launched a selective crackdown.

Xinhua quoted experts including professors at the party's central school as saying any political reform would aim at "strengthening, not weakening" the organisation's leadership.

Cai said that, ultimately, economic reform cannot truly succeed without changes to how the government acts, such as reducing local authorities' interference in business.

"You can talk about all sorts of economic policy changes, in the end whether these policy changes will make a serious impact on the Chinese economy really depends on whether we will have serious government reforms," he said.

China's leadership says the economy, the world's second largest, needs to move away from reliance on state-financed investment projects and unleash the power of consumers and other private actors to propel growth.

The country recently launched a much-publicised free-trade zone in Shanghai, but has not specified deadlines for key reforms in it, including unrestricted currency flows, a government document seen by AFP showed, suggesting changes will be step-by-step.

Yao Wei, Societe Generale economist in Hong Kong, said Xi's tenure had shown some promise, with moves to free companies from "the visible hand of the state".

But a "roadmap with some idea of timeframe" might be the best that can be hoped for from the plenum, she wrote.

She added: "The real test of Beijing's reform resolution will be the action taken in the following three to six months."