PRESSURE is mounting for the Government to declare a timetable for enacting electoral changes for the 1994/95 elections or to reveal what China and Britain have discussed about them in two rounds of talks in Beijing. Next week will be tough for the Governor, Mr Chris Patten, who will have only just completed a busy week-long mission to the United States. On Wednesday, the Reverend Fung Chi-wood will formally ask the Government during the Legislative Council sitting to provide more information about the Sino-British talks. The same day, Mr Lu Ping, who as Director of the State Council's Hongkong and Macau Affairs Office is Mr Patten's counterpart on the mainland, begins a three-day visit to Macau during which he is certain to make full use of media opportunities to attackMr Patten's proposals. On Thursday, Mr Patten faces legislators' queries about his trip to Washington, which Beijing believes was an attempt to lobby US support for his political blueprint. The following Wednesday, United Democrats vice-chairman Mr Yeung Sum will demand that the Government tell Legco whether it is still committed to having legislative arrangements for the 1994/95 elections in place before the end of the legislative sessionin July. That question will be posed two days before the third round of Sino-British negotiations begin in Beijing. The two sides are still locked in disagreement on matters of principle, such as how legislators might qualify to be able to ride the so-called ''through train'' from 1995 to beyond 1997. Mr Yeung will turn up the heat three days after the third round of talks by forcing a debate on the need for the Government to disclose the progress and agenda of the negotiations, as a means of increasing their transparency. In Beijing, the British Ambassador to China, Sir Robin McLaren, refused to comment on remarks made on Wednesday by Mr Lu about the previous two rounds of talks. Sir Robin cited the agreement on confidentiality and added that he would abide by it. But he was confident that the meeting between Mr Patten and the US President, Mr Bill Clinton, in Washington earlier this week had not undermined the Beijing talks. A Chinese Foreign Ministry spokesman, Mr Wu Jianmin, said China denounced any attempt to ''internationalise'' the Hongkong issue, which he said would not succeed. He said it was up to the British and Chinese Governments to decide on the resumption of talks at the Sino-British Joint Liaison Group (JLG). However, Sir Robin said he hoped the JLG could meet as soon as possible. The Secretary for the Treasury, Mr Yeung Kai-yin, yesterday said no date had been fixed for resuming talks of the JLG Airport Committee. He also rejected the suggestion that a meeting could not be held until the British side had put forward another financial package. Noting that there were some encouraging remarks from China recently on resuming talks, Mr Yeung said: ''We are ready to take discussion forward on the financial packages as soon as it becomes possible to do so on their merits, so we welcome what the Chinese officials have said. ''If there is something substantive to talk about, we are ready to meet at any time, whether we propose something or they propose something.'' Despite the postponement of work on the Chek Lap Kok airport and its associated railway project when the two sides failed to reach a deal on the financial arrangements, Mr Yeung said he was confident the two projects would be built sooner or later. ''We are still trying within our present constraints to do what we can. We believe there is still scope of finishing the entire programme on time, but with every day of non-decision, the risk of that target date being missed will become greater,'' he said. Meanwhile, Mr Wang Hanbin, a vice-chairman of the National People's Congress, yesterday told a delegation from the Association for Democracy and People's Livelihood that half of the membership of the proposed working organ for the establishment of the SAR Preparatory Committee would be Hongkong residents.