TALKS between the mainland and Taiwan on hijacking, repatriation of illegal immigrants and fishing disputes remained deadlocked yesterday over the underlying principle of whether Beijing would acknowledge Taipei's right of legal jurisdiction. Negotiators from both sides were burning the mid-night oil last night, hoping to iron out their differences and pave the way for Tang Shubei, Vice-Chairman of China's Association for Relations Across the Taiwan Strait (ARATS), to visit Taipei before the end of the year. The two sides are expected to meet again today. Hsu Hui-you, chief negotiator for Taiwan's Straits Exchange Foundation (SEF), said little progress towards an agreement on repatriation of illegal immigrants was made due to differences over ''basic principles'' involving sovereignty and legal jurisdiction. ''The differences lie in the gaps between fundamental ways of thinking on the two sides,'' Mr Hsu said. The mainland side reiterated its demand to send public security officials to check on the identity of the nearly 2,500 illegal immigrants held in Taiwan instead of carrying out such identification work upon repatriation, he said. Mr Hsu said Taipei could not accept this demand because it violated Taiwan's legal jurisdiction and was not reciprocal. Progress towards a hijacking agreement was stymied by a similar argument. The mainland side maintained that hijackers should be sent back where they ''reside'', regardless of their citizenship. Taiwan's SEF insisted that dual residency by many Taiwanese made this impractical and that the definition should be made on the basis of citizenship. Similarly, the two sides could not agree on the legal status of a proposed deal to arbitrate fishing disputes. Meanwhile, Taipei yesterday appeared to be reconsidering an invitation sent to Mr Tang to visit Taipei just as the ARATS Vice-Chairman expressed his acceptance. SEF Vice-Secretary-General Lee Ching-ping announced yesterday that ARATS had faxed a letter indicating Mr Tang's wish to visit Taipei for five days before the end of the year. The ARATS message said Mr Tang wanted to discuss a possible visit by SEF Chairman Koo Chen-foo to Beijing next year. However, SEF Secretary-General Chiao Hen-ho indicated Taipei was reconsidering the timing of Mr Tang's visit due to the lack of progress in talks.