The session, which will bring together more than 300 members of the party's central committee, is expected to take steps to implement policies outlined at the 16th party congress last November.

Analysts said the plenum is expected to discuss outlines for economic reforms and the nation's opening up over the next 10 years, with the aim of China becoming more open to the outside world and to raise the living standards of the people.

It is likely to discuss ways to strengthen protection of private property, although the politburo said public ownership was to remain at the centre of economic life.

The constitutional amendments are likely to be minimal, as the politburo has termed the present structure 'a good constitution'.

This suggests that any changes that are introduced will be confined to adapting to the demand for reform, opening up and modernisation.

The Theory of the Three Representatives, the brainchild of former president Jiang Zemin, is widely expected to be written into the constitution, which has been amended four times since 1982.

Mr Jiang's theory, which says the party represents all the advanced elements in society including the private sector, was written into the party constitution at the 16th congress.

However, the idea of strengthening protection of private property rights has sparked controversy over whether the degree of protection should match that for state property, which is deemed 'sacred and inviolate'.

The politburo has appeared to be bowing to opponents of the reform by affirming the central role of state property in economic life.

By implication, private property will probably be relegated to a secondary role.

The constitutional amendments, once approved by the third plenary session, will be sent to the standing committee of the National People's Congress for a review to be carried out.

Political observers noted that since the third plenum of the 11th party congress under Deng Xiaoping's leadership in 1978 became the landmark for reform and opening up, the anticipation for each third plenum since then had remained high.

President Hu has placed strong emphasis on the rule of law and, along with Premier Wen Jiabao, proved his determination in the handling of the Sars crisis.

The plenum will also give the new leadership an opportunity to review economic performances for the year and map out economic growth targets for next year.

Revitalising the old industrial base in the northeast is likely to be high on the agenda.

Mr Wen has chaired a conference in Changchun, Jilin province, on this theme and provincial officials have openly discussed the proposed development strategies.