HONGKONG'S sewage treatment strategy may turn into another thorny issue between the Chinese and British governments, following Budget proposals to inject $4.9 billion into the massive programme. Mr Macleod proposed in the Budget to put an extra $1.9 billion into the programme, in addition to the $3 billion promised by the Governor last October. Under his plan, the scheme will be expanded to include the Central and Wan Chai sewerage master plans at a cost of $1 billion. Another $900 million will be invested to keep charges as low as possible. Pro-China legislator Mr Tam Yiu-chung yesterday questioned whether the Government had China's blessing for the project, which will straddle 1997. ''Now the Hongkong Government is even proposing to inject an additional $1.9 billion into it,'' he said. ''I am very sceptical about this. China has not given its blessing on the massive programme up to now and the Government should think seriously about it. ''If China opposed the programme, it would mean throwing taxpayers' money into the deep sea.'' Mr Tam and four members of the Democratic Alliance for the Betterment of Hongkong will meet the director of the Environmental Protection Department, Dr Stuart Reed, tomorrow to voice their concern. The convenor of the Legislative Council panel on environment affairs, Mr Peter Wong Hong-yuen, said he hoped the issue would not be politicised. ''I welcome any spending to improve our environment,'' he said. ''The only hope I have is to let the programme go ahead, but not to be politicised. ''So, if there is a Sino-British agreement on the airport and political reforms, I believe the programme could be spared.'' Meanwhile, the Government intends to invite private investment to construct the $9 billion country park section of Route 3 Highway under a build, operate and transfer franchise. Mr Macleod promised that the Government would earmark $4 billion to attract private involvement in building the road. The Government said in a paper given to Legislative Council transport panel members yesterday: ''In essence, [consultants] have confirmed that the project could be attractive to the private sector and have recommended that, as a first step, expressions of interest should be invited.'' The build, operate and transfer franchise scheme allows private finance and construction of a project with repayment through toll collection for a set term, before the project reverts to government control. The country park section, which runs from Tsing Yi to Au Tau, involves the building of a bridge from Tsing Yi to Ting Kau and a tunnel under Tai Mo Shan. The Secretary for Transport, Mr Michael Leung Man-kin, said a 30-year lease would be granted. The country park section could be finished by late 1998 or early 1999.