CHINA'S impoverished northwest has made a bold bid for a bigger share of the economic pie. Leaders of the five northwest provinces of Shaanxi, Gansu, Qinghai, Ningxia and Xinjiang held an unprecedented summit recently, in which they agreed to join in efforts to get more favourable policies from Beijing. The regional bosses also pledged to ''join hands in tapping local natural resources and developing local economies'', according to a Xinhua (New China News Agency) dispatch yesterday. The cadres indirectly blamed the low level of development in their areas on a lack of investment and Beijing's policy of favouring the southeast coast. The party secretary of Shaanxi, Zhang Boxing, complained about the shortage of funds for infrastructure. ''Although Shaanxi is rich in natural resources, many of the resources remain untapped due to poor transport and telecommunications facilities,'' he said. Yan Haiwang, the party boss of Gansu, lobbied for more central funds for irrigation as well as economic help from the coastal provinces. He suggested Beijing build more water conservancy projects in his arid province and that more ''aid-the-poor policies'' be enacted. In private discussions, other officials expressed the wish that the central Government give them more leeway in experimenting with market forces. Xinhua reported that the top cadre of Ningxia, Huang Huang ''encouraged local officials to do away with the vestiges of the centrally planned economy and enhance the sense of the market economy''. Economic analysts said many of the ''vestiges'' had been imposed by central planning-oriented cadres in Beijing. The conference ended with pledges by the leaders to explore the possibility of an ''economic co-operative zone'', which could form the basis of a regional power bloc. The analysts said cadres from the northwest might find support in Beijing, which had already pledged unprecedented levels of aid to the region. They said Beijing was anxious to narrow the gap between west and east. Meanwhile, leaders of rich areas such as Guangdong and Hainan have expressed fears about losing preferential policies they have enjoyed since the mid-1980s. Xinhua yesterday quoted leaders of Guangdong as saying they must lift the province's open door policy ''to a higher plane''. And Hainan Governor Ruan Chongwu said yesterday provincial cadres had to ''boost the strength of reform and expand the open door policy''.