CHINA'S Prime Minister Li Peng assured regions yesterday that their interests would be protected during a crucial national work conference on the pace and scope of reform to be undertaken next year. The conference, for the first time attended by State Council leaders, provincial and department heads, follows the passing at the party's third plenum last month of a blueprint for building a socialist market economy. Some analysts see the four-day meeting chaired by Vice-Premier Zhu Rongji as a round of bargaining between central and provincial heads on the nitty-gritty of the new reforms. One bone of contention will be how to implement a new tax-sharing formula between the central and local authorities, singled out by Mr Li as one of the three ''major steps'' next year to revamp the fiscal and tax system. The others are the setting up of a new tax rate and the allocation of profits from state-owned enterprises. Mr Li told the conference that the reform blueprint would take into account the reality of China while copying the common practice in other affluent countries. ''Reform will consider the needs of gradually increasing the total financial strength of the central Government and, at the same time, cater to the needs of the regions and the operation of enterprises,'' he said in a Xinhua (New China News Agency) despatch. A researcher at the State Development Centre, Professor Yang Peixin said a joint conference would avoid problems from the lack of co-ordination among various departments. ''The blueprint adopted at the third party plenum is just a skeleton outlining long-term goals. To what extent the goals will be met next year will have to be decided at the conference,'' he said. Mr Li described 1994 as an ''important year'' for the maintenance of the ''good momentum'' for economic development achieved this year and a ''critical year'' to push ahead market economy reforms.