GENEVA (Reuters) - Arms negotiators failed to clear the way on Monday for the start of talks this year on nuclear disarmament as Pakistan said its security interests had not been respected. Efforts will now focus over the coming months on trying to find a way to allow the UN-sponsored Conference on Disarmament to start substantive work in January, diplomats said. The window of opportunity for this year is closing today, Austrian Ambassador Christian Strohal, the current president of the conference, told the 65-member forum. It is with serious regret that I have to inform the conference that consensus ... still eludes us. The conference, which is the worlds sole multinational forum for negotiating disarmament, broke a 12-year stalemate in May when it agreed a work plan to start negotiations on banning production of fissile material for nuclear bombs. It also agreed to discuss three other issues - general nuclear disarmament, prevention of an arms race in outer space and negative security assurances, where countries promise not to use nuclear weapons on non-nuclear-weapon states. But the next step, agreeing the implementation of the work plan so that different working groups could start examining the various issues, has proved impossible to achieve. Diplomats said the current stalemate was all the more frustrating as the May agreement had shown the conference could work together, uniting Western countries, Russia, China, the Middle East, Latin America, and even Iran and North Korea. Pakistan, which tested a nuclear weapon in 1998, says the implementing proposals could threaten its national security. Its main concern is that the proposals would have the negotiations focus on the fissile material treaty, and not seek results in the other three areas, which it says are equally important. We wanted to see a programme of work being implemented in a way that would set the stage for a balanced outcome on all the four issues, Pakistani Ambassador Zamir Akram told Reuters. He said Pakistan was backed by other countries in the Non-Aligned Movement, and noted that China and Russia were also keen to see progress on an arms ban in outer space. The May breakthrough followed a shift in US arms policy under President Barack Obama, who has made it clear he wants nuclear and other disarmament to advance with US involvement. Akram said that, as a result, the conference should tackle the whole range of issues. We see the change that took place in US policy on the overall question of arms control... as a positive step in getting a window to progress in all the issues, he said. The way the United States, Russia, Britain and France appeared to be steering the fissile material treaty was also of concern to Pakistan, Akram said. These four official nuclear powers - the fifth being China - want the treaty to focus on non-proliferation, in other words banning the future production of fissile material, he said. But Pakistan feared such an approach would not take account of existing stocks, putting recent nuclear powers such as Pakistan at a disadvantage to the more established ones. Next months UN Security Council summit on nuclear disarmament and the regular discussions on disarmament in the General Assemblys First Committee later this year will provide an opportunity for other powers to find a way to overcome Pakistans reservations, diplomats said. With the current conference session due to end on Sept 18, there would have been little time for substantive negotiations, which would have to start in earnest next year anyway. It would have been largely symbolic. The practical effects would not be huge. We will have to come back to it in January, said one Western ambassador.