AS the Soviet Union disintegrates, both Soviet and Western leaders are haunted by the breakup of a huge, nuclear-armed Soviet military.Russian President Boris Yeltsin, addressing the Congress of People's Deputies Sept. 3, tried to calm fears that the Soviet nuclear arsenal would get out of control. "Russia will guarantee that the nuclear potential does not fall into the hands of either hawks or extremists," he said, adding that structures to do this were being formed now. The leaders of the Soviet republics, who now collectively run the country, have been quick to declare their agreement that a united Army with control over nuclear weapons should continue to exist. But beyond that commitment in principle, little consensus has been reached on what this may mean in practice. The proposal for organization of a transitional Soviet administration, presented Sept. 2 by the republics and President Mikhail Gorbachev, calls for signing an agreement "to preserve united armed forces and ... to carry out radical military reforms in the armed forces ... taking into account republican interests." "We shall have a joint, military-strategic space and the strategic [nuclear] forces shall operate in all the corners of this space," Yvgeny Primakov, Gorbachev's national security advisor, told the Monitor. "But at the same time, ... some actions should be discussed with [the] republics." "Every Soviet citizen, as well as every American citizen, is worried about the unity of the Army," said Air Force Maj. Gen. Pyotr Klimuk, a cosmonaut and People's Deputy. "If the Army is torn apart by the republics, it is difficult to predict where that might lead." But military leaders are unclear as to what the republics mean when they refer to keeping a single Army. "They are saying that the Army we have now has to be preserved," said General of the Army Stanislav Postnikov, commander of the Western Theater. "There are some hints that some sort of a [republican] national guard will be created, but that is still in the air," he said. Even the idea of a national guard is far from clear. For some, it suggests a several-thousand-man force, devoted mostly to internal security and protecting frontiers. But Ukrainian President Leonid Kravchuk, in a Sept. 2 press conference suggested it would work as a full-scale army. That idea is unacceptable to the Soviet armed forces leadership. "The Army basically should be united and should be subordinated to one, central command, because it implies certain consequences, primarily for the command of strategic nuclear weapons," Col. Gen. Bronislav Omelichev, first deputy head of the General Staff and a People's Deputy, told the Monitor. "If there is a strong desire to create republican armies, this has to be solved in the framework of a single, union Army, with republican armies p erforming certain tasks necessary to defend these sovereign republics." Other ideas are circulating. Gen. Vladimir Lobov, the newly appointed Chief of the General Staff, suggested in a Sept. 2 newspaper interview, that the national guard would consist of the Soviet troops based on the territory of a republic, wearing both the national insignia and republican emblems. He proposed that 60 percent of all conscripts serve in their own republic, making up most of the troops stationed there. The content of proposed "radical reform" is equally fuzzy. According to Maj. Gen. Klimuk, the new defense minister, Air Marshal Yevgeny Shaposhnikov discussed his reform ideas with the military deputies at a closed meeting Sept. 2. While not revealing the content of that discussion, General Klimuk said the ideas include proposals that "each republic should have a partial say in financing the Army. We should clearly define what kind of Army we need - we need an Army not to attack but to defend the borders of the country." The unresolved issues include the scale of conscription and the years of service, Klimuk said. "Reform should be carried out boldly, resolutely, and swiftly, but not recklessly," General Lobov told the Nezavisimaya Gazeta. General Lobov proposed that the minister of defense be a civilian and that the armed forces be jointly run by the commander-in-chief, the Soviet President, and by the General Staff. The civilian minister would deal with military supply problems and infrastructure, he explained, while the general staff would be responsible for training and operation of armed forces. "I hope the new structure of the Army will to a significant degree suit everybody and all the republics will participate in it," Lobov said. "The single economic space should be protected by a single defense space."