UN peace plan for Falklands: 'no winners, no losers'

''Will Britain and Argentina settle for a tie? That is the question,'' says one high United Nations official, paraphrasing Hamlet.

A deal between Argentina and Britain allowing them to stop fighting over the Falkland Islands may be at hand. It is both honorable and fair to both nations, according to many impartial observers here.

It could be struck in a matter of days, perhaps this weekend. And yet it may prove elusive.

A package, worked out by UN Secretary-General Javier Perez de Cuellar and patiently negotiated during close to 20 rounds of intensive talks with both parties, would allow Argentina's Gen. Leopoldo Fortunato Galtieri and Britain's Prime Minister Margaret Thatcher not only to save face. The plan would also enable the two leaders to claim that they have not surrendered on matters of principle.

''No winners, no losers.'' That is the Perez de Cuellar formula.

But one Western diplomat with experience in crisis management warns: ''The real question is not whether London and Buenos Aires will agree to Perez de Cuellar's plan, but whether they will do so before the week is over and before more blood is spilled, or in a week or two when both sides have convinced themselves that they cannot get more at the bargaining table than their military might can obtain on the ground.''

Whether the future of the Falklands will be settled peacefully through a proposed UN mechanism, or whether it will involve still more fighting, will depend, according to informed sources, on:

* Whether both sides think they can still get a better deal after a new round of shooting.

* Whether they will consider the fig leaf provided by the UN as large enough to salvage their prestige at home.

Intensive face-to-face negotiating rounds in the last few days -- involving Perez de Cuellar and Argentine deputy Foreign Minister Enrique Ros, on the one hand, and the Secretary-General and British delegate Sir Anthony Parsons on the other hand -- can thus be interpreted in two different ways, according to one informed diplomat:

1. The military pressures that those countries are now applying to each other may be aimed at softening each other up at the UN negotiating table.

2. The UN talks are but a smokescreen -- a play for time during which Britain and Argentina ready themselves for the next battle.

The UN plan on which all peace hopes now rest provides for a cease-fire, a simultaneous and gradual withdrawal of Argentine forces from the islands and of the British fleet from the area, the establishment of a temporary UN administration over the islands and negotiations under the auspices of the Secretary-General within a time frame (somewhere between 6 and 12 months) on the question of sovereignty over the Falklands.

There can be no doubt as to the fact that both Argentina and Britain have mellowed their initial stance considerably as a result of Perez de Cuellar's gentle but persistent prodding. Argentina no longer insists that a solution explicitly recognize its sovereignty over the islands. Britain no longer demands that the islanders be allowed to determine the future of the Falklands.

Indeed, Argentina could claim that the deal does not provide for a return to the status quo ante, and to what it calls ''a colonial situation.'' Britain could claim that ''the aggressor has not been rewarded'' and that ''diplomacy, not force, will determine the future of the islands.''

Both Britain and Argentina would be settling for less than what they publicly demanded. At this point, according to a high Western official, ''Both British and Argentine leaders have come to realize that eventually the Falklands will become Argentinian but that its inhabitants will have to be granted strong minority rights. For obvious geographical, economical, political, and strategical reasons there is no other way to solve the problem in the long run. So what is at stake now essentially is face-saving.''

A senior Latin American diplomat says: ''There is no other reasonable way out for Argentina and Britain than the one offered by Perez de Cuellar. The two countries can inflict serious wounds on each other but neither can hope to put the other one out of commission. Perez de Cuellar's package allows the two boys to go home and to say that they won the fistfight.''

Perez de Cuellar's extremely detailed package plan is particularly ingenious in as much as he does not attempt to settle the future of the Falklands. It rests on Article 40 of the UN Charter, which provides for ways and means by which the UN can temporarily take control of a disputed area and force those who claim it to negotiate their dispute, without in any way prejudging the issue.

The trouble appears to be that while both sides have extraordinary trust in Perez de Cuellar's impartiality, by their own admission, their mistrust of each other is abysmal and that while tempted by the bargain they are afraid to be trapped.

''To bridge the cultural gap between the traditionally perfidious British diplomacy and the somewhat crude, primitive mentality of the Argentine military is not an easy task,'' says a well-placed source.

Yet Perez de Cuellar has on past assignments before he became Secretary-general been able to draw closer such parties as the Rhodesian white settlers and the now Prime Minister of Zimbabwe Robert Mugabe, Turk and Greek Cypriots, pro-Soviet Afghans and pro-American Pakistanis.