THE Government's piecemeal approach to building the Chek Lap Kok airport will reach a crucial stage in May when construction of the multi-billion-dollar terminal is scheduled to begin, legislator Samuel Wong Ping-wai said yesterday. He said the project could not proceed without extra government funding or an overall financial arrangement with China. ''New projects cannot proceed after May, as the contract for the airport building cannot be split bit by bit,'' he said. Mr Wong believed the Government should pay for the project from the $200 billion surplus it is expected to have accumulated by 1997. He said contracts so far approved by legislators were all within the scope of the Government's intended funding of $16.6 billion stated in its original financial package. This month legislators approved a funding request of $1.67 billion for three urgent airport-related contracts and a full year of running costs for the Provisional Airport Authority (PAA). According to Mr Wong's estimates, the Government would need to inject $13.5 billion more in order to satisfy China's wish to confine all borrowing within the ceiling of $5 billion. He said sharp increases in land values along the proposed airport railway had narrowed the amount of additional money required. While China insists the $5 billion borrowing ceiling stated in the Memorandum of Understanding on the new airport included borrowings by the PAA and the Mass Transit Railway Corporation, Hong Kong officials insist the $45 billion in debts arising from thetwo corporations should not be counted as government borrowings. The Government said in its latest financing package that it was willing to inject $45.3 billion into the projects. But it would still require $45 billion of borrowings by the PAA and the MTRC to fully fund the projects. The Executive Council will discuss new financing proposals tomorrow.