CALL it "just do it" arms control.By vowing to make unilateral reductions in US nuclear weapons and asking the Soviets to follow suit, President Bush last week took an approach to arms talks that would have been unthinkable only months ago. It seems likely to prompt results: Meetings on the proposals will begin in Moscow next week. An aide to Soviet President Mikhail Gorbachev said Tuesday that "it would be a sin" to miss this historic opportunity to reduce weaponry. But the Soviets will want to broaden the agenda beyond items that Mr. Bush has proposed. They hope to put the nuclear arsenals of France and Britain on the table for discussion and entice the United States into setting limits on nuclear testing. The US has long resisted Soviet attempts to negotiate a test ban. In the new post-coup spirit of cooperation, however, US officials indicated this week that they would listen to anything the Soviets want to bring up. Bush's initiative will "reduce our nuclear deterrent to make it smaller, safer, and more stable. And this could perhaps have some impact on nuclear testing," State Department spokeswoman Margaret Tutwiler said. Compared to the old way of conducting arms control, the events of the past few days have moved with breathtaking speed. The just-completed START treaty limiting long-range weapons, for instance, took nine years of negotiations, is hundreds of pages long, and details methods for 12 kinds of on-site inspections. The Conventional Forces in Europe pact goes so far as to list criteria for destroying tanks with explosives. By contrast, President Bush simply ordered all US tactical missiles and shells out of Europe with a sweep of the hand and called on the Soviets to do the same. It's true that the weapons involved had lost much of their military utility with the fall of Eastern Europe. But combined with the unilateral removal of all nuclear weapons from Navy surface ships it represents a significant move. It violates one of the past primary principles of arms control: Never give up something for nothing. If the moves herald a shift toward informal arms agreements, "it means arms control can happen a lot faster," notes Greg Weaver, a senior weapons analyst at SAIC Corporation. Gorbachev aide Andrei Grachev hinted this week that the Soviet Union would make a similar dramatic reduction in tactical nuclear arms. It's an area Moscow has long wanted cuts in, and with many of these weapons stored in fractious republics it could make the Kremlin and the White House breathe easier. Not everything Bush proposed last week was unilateral. One major part of his arms initiative calls for talks on banning ground-based multiwarhead (MIRV) missiles, an area where the Soviets have a superior arsenal. Mr. Gorbachev so far has not given a specific answer to this offer, but he will likely call for similar limits on submarine-carried, multiwarhead missiles - an area of US advantage. The Soviets have also long wanted to bring the French and the British into discussions of nuclear limits. And US officials are hinting this may now be possible: One scenario has Bush, Gorbachev, British Prime Minister John Major, and French President Francois Mitterrand meeting in a four-way summit in the fall. One thing Bush didn't mention in his proposals was any new, lower limit on strategic warheads. The START pact calls for reductions of around 30 percent from current levels, down to some 9,000 weapons for the US and 7,000 for the Soviets. (Permissive rules for counting bombs account for the difference.) Arms control activists have been pushing for warhead cuts of 50 percent or more. Yet complete elimination of land MIRVs would still leave the US with 8,500 long-range nuclear weapons, figures Lee Feinstein, research director of the Arms Control Association. "If we don't seize the opportunity now to make truly deep cuts, I'm concerned it will pass us by," he says. Though the Soviets have yet to reveal their detailed reaction, Bush's proposals are already having repercussions elsewhere in the world. Dutch officials, for instance, announced plans to end their nuclear contribution to NATO defenses. The Dutch have no nuclear arms of their own. In war, NATO doctrine had called for Dutch anti-submarine planes to carry US nuclear depth charges. Defense Ministry spokesman Hendrik Shoenau said on Tuesday that this role would be ending, citing Bush's pullback of tactical nuke arms. In New Zealand officials said that Bush's moves could cause them to reconsider their ban on visits by US Navy ships that carry nuclear weapons or are powered by nuclear reactors. This ban caused the US to end defense cooperation with New Zealand in 1986, since the Pentagon refuses to confirm or deny the presence of atomic arms on ships.