THE progress of Beijing's new think-tank on the territory's economic affairs has been hampered by the Government's lack of co-operation. The Preliminary Working Committee's (PWC) economic sub-group has decided to cancel its full session on Wednesday and Thursday in the wake of a Hong Kong Government decision not to send officials to Beijing to explain the controversial Airport CorporationBill. It has also been revealed that the panel had difficulty in understanding and collecting information about the bill, which was announced early this month. Fears have also been raised that the think-tank will not be able to provide suggestions to Beijing on time - the consultation period of the bill will finish at the end of next month. The economic sub-group invited the Secretary for Economic Services, Gordon Siu Kwing-chue, to attend its meeting in Beijing to explain the bill three weeks ago. But the Government refused and Mr Siu cancelled a scheduled trip to the Chinese capital to sign an accord under which Hong Kong would provide training for the Provisional Airport Authority. The next meeting is scheduled to be held by the end of February, the deadline for the end of consultation period. As no conclusion was reached during the last meeting three weeks ago, it is likely the panel will not be able to advise the Chinese side about the issue on time. PWC member Tam Yiu-chung acknowledged some members of the panel found difficulties in understanding the Airport Corporation Bill. ''As a Legislative Council member, I can ask the Government about what I need to understand about the bill. However, for some members who are not HKMAO [Hong Kong Macau Affairs Office] officials, it would be rather hard for them to understand,'' he said. It is expected the sub-group will rely on its legislators and Airport Consultative Committee members for information about the bill. The sub-group has several questions on the article concerning the relationship between the Government and the Airport Corporation, and the composition of the company.