The United States has proposed to its European allies that the controversial neutron bomb be used as a bargaining chip in an effort to get the Soviet Union to halt deployment of its SS20 mobile missile.

The secret strategy, according to sources at the North Atlantic Treaty Organization headquarters here, calls for an effort to win concessions from the Soviet Union in exchange for agreement not to proceed with the new American weapon.

The United States, sources say, would agree to call off production of the neutron bomb and the NATO allies would agree to forego its deployment only if the Soviet Union would agree to either retire its new intermediate range SS20 mobile missile, which is targeted on Western Europe, or reduce Warsaw Pact troop levels.

If the Soviets reject those offers, as many U.S. officials expect, it will then become easier politically to go ahead with both production and deployment of the weapon, sources [TEXT ILLEGIBLE] strategy for "arms controling" the neutron weapon.

Part one is said to be bilateral negotiations between Washington and Moscow, involving a direct tradeoff between the neutron warhead and the Soviet Union's SS20.

Defense analysts here, however, privately query the "symmetry" of negotiating the neutron warhead against the SS20 which, unlike the neutron weapon, is not a tactical battlefield weapon but a medium-range ballistic missile with three independent nuclear warheads.

The second option suggested by Gelb, sources said, is for NATO to put the neutron weapon on the table of the troop reduction talks currently stalled in Vienna. Here again, there seems no obvious parallel bargaining counter that the Warsaw Pact countries could offer in exchange, unless it was a commitment to reduce their current level of tank superiority.

In this scenario, negotiators would have two years - the time needed to produce the neutron weapon - to get the Soviets to agree to concessions. If these were not given, deployment would follow.

But the American proposals may run into difficulty with some of the Europeans, in particular the Scandinavians and Dutch. Wednesday the Dutch parliament voted against the production of the neutron warhead under any circumstances. Dutch sources say that putting the neutron weapon up for arms control negotiation, implying a go-ahead for its production, would be difficult for a Dutch government to accept.

Yet the American formula could gain political acceptance in Britain and West Germany. British Prime Minister James Callaghan told the House of Commons on Feb. 21 that "the neutron bomb is a weapon that is feaful in its use but no more fearful than a number of weapons now being developed by the Soviet Union, including the SS20, for example," adding that "we should not tackle this from the point of view of a single weapon."

The neutron weapon issue is seen here as certain to be discussed at the next meeting of the alliance's nuclear planning group, to be held in Denmark in mid-April. Meanwhile, it is clear that the Americans want the decision on the neutron warhead out of the way before the NATO summit meeting scheduled for Washington May 30-31.

At the disarmament conference in Geneva yesterday the Soviet Union and its Warsaw Pact allies proposed a ban on the neutron warhead. The U.S. delegate called the move a "one-sided propaganda exercise" and challenged the Soviet Union to discuss the SS20 missile.