IGNORING international criticism of its nuclear weapons test, China has pledged to continue with its limited nuclear development programme at the top secret Lop Nor test site in the remote northwestern region of Xinjiang. ''China will continue to exercise the utmost restraint with regard to nuclear testing,'' Foreign Ministry spokesman Wu Jianmin said in Beijing yesterday. Mr Wu played down fears that China's underground test on Tuesday could trigger a new round of nuclear tests from other nuclear powers, saying how other countries managed their test programmes was ''their own business''. Speaking at his weekly press briefing, Mr Wu reiterated China's commitment to the early conclusion of a comprehensive test ban treaty but again warned that such a treaty would be of little significance unless accompanied by a global agreement on the non-first-use of nuclear weapons. ''China maintains that parallel negotiations by all the nuclear powers on the conclusion of an international convention on the non-first-use of nuclear weapons and the non-use of nuclear weapons against nuclear free countries and zones are even more important [than a test ban treaty].'' ''China, out of all the nuclear powers, has taken the lead in this respect,'' Mr Wu said, adding that immediately after its first nuclear test in 1964, China gave a comprehensive guarantee that under no circumstances would it be the first to use nuclear weapons. He went on to point out that of all the five nuclear powers, China's test programme was by far the most limited, amounting to just 39 tests in the past 29 years, compared with 942 by the United States since 1945. While China has incurred the wrath of the Western powers for breaking the informal moratorium on nuclear testing suggested by the US, many independent observers said such criticism was unwarranted. ''It's clear that China's nuclear weapons programme is the smallest and least sophisticated of all countries with nuclear weapons,'' a senior Asian diplomat said. ''I think China has a very legitimate need to upgrade its systems, particularly given the continued [perceived] threat from the US.'' In Taiwan, the Kuomintang Government condemned China's underground nuclear test, accusing its arch-rival of threatening global security. ''This move by communist China violates the widespread international trend of banning nuclear tests . . . ignores world opinion . . . and threatens global security,'' government spokesman Jason Hu said. Meanwhile, China has announced it has developed a Tokamak-type nuclear fusion device, becoming only the fourth country in the world to master such technology, Xinhua (the New China News Agency) said. France's Defence Minister Francois Leotard said yesterday Paris would have to carry out a limited number of small nuclear tests at future unspecified dates before signing a possible international test ban treaty. ''Our nuclear deterrent is not threatened by our current halt in tests and will not be for a long time,'' he said. Tokamak-type fusion devices were first developed by the former Soviet Union in the 1960s and are viewed as a possible way of generating electrical power with nuclear fusion. Current nuclear power plants use fission instead. Development of commercial fusion power plants is still far away.