By the time the leaders of the seven richest nations of the industrialized West gather here next week, the communique to be released at the end of their three-day summit will already have been written.

By common accord, put together by aides known in the world of summitry as "sherpas," it will be short and, in the words of one official, "thin gruel." But the job of the sherpas, the official said, "is to make it sweet gruel rather than bitter."

Despite the ritual of shared democratic values to be played out at Versailles, rarely has there been so much offstage fear and loathing in the ranks of the latter-day peers of Louis XIV, for whom the ultimate in monarchical splendor was built.

In attendance at Versailles will be the United States, Britain, France, West Germany, Canada, Japan and Italy.

In European eyes, the chief culprit, the party responsible for the problems and the divisions among the seven nations who first met in nearby Rambouillet in 1974, is President Reagan. It was his administration's policies they first criticized at last year's summit in Ottawa. Despite American promises, they say, there has been little remedy.

"The only difference," said a former minister close to past summits, "is that this year the complaints have crossed the Atlantic and half the United States is echoing what Europe was saying even then."

No one in Europe questions the Reagan administration's reasons for fighting American inflation. But many here feel that the high interest rates they have been clamoring about now are due to the president's gaping federal budget deficit, not the government printing press.

Just beneath the surface of European anguish is the nightmare scenario in which democratic institutions fall apart on the old continent not from a Soviet military onslaught or domestic subversion but from economic and monetary warfare among the noncommunist nations.

Nowhere are such fears more widely held than in France, which in the past year has abandoned prickly Gaullist nationalism for a more pragmatic transatlantic approach. In view of the pacifism rampant in much of Europe, France's Socialist leaders reason that Paris is Washington's top ally and has proved it in political and military terms by a shared concern about the real nature of the Soviet threat.

But the French fear that Reaganomics is undercutting the new-found amity and helping nurture the very anti-Americanism that the Socialists sought to blunt.

A recent American willingness to study possible intervention on volatile foreign-exchange markets--a longstanding European request that Reagan administration aides originally rejected--has brought temporary calm on that score. Informed sources maintain that intervention in the currency markets is but one aspect of a general agreement to revamp the much-neglected international monetary system, which will be announced at the summit.

On the equally thorny issue of Western credit policy toward the Soviet Union and its satellites, even France, as one of the most outspokenly anti-Soviet European powers, does not share the Reagan administration's zeal for using East-West trade to pressure the Soviets.

European politicians--and many American officials, albeit in private--make no secret of their fears that any such approach, perhaps even including renewed efforts by Washington to try to stop the Siberian gas pipeline deal, could touch off a wave of anti-Americanism that principally would benefit the Soviets.

Confronted with such an unpleasant prospect, sources here said that French President Francois Mitterrand will suggest that his partners cooperate on high technology as a way to solve the economic crisis and work together in the future. The project was conceived as one that all capitals could accept, although the original French draft's stress on government investment in such cooperation was altered to reflect an American desire to provide a role for private capital as well.

Whatever the eventual fate of Mitterrand 's centerpiece project, the familiar unresolved problems of past summits will remain as unappetizing as ever.

France and Italy still want priority treatment accorded unemployment--industrialized jobless grew from 25 million to 30 million between summits--but the other participants, to varying degrees, endorse Reagan's anti-inflation position, if not his method of implementation.

With Britain fighting Argentina over the Falklands--the first time a summit country has been at war since the meetings began--Prime Minister Margaret Thatcher is expected to keep a low profile.

Other now-standard bones of contention are the Reagan administation's reluctance to endorse the new North-South order that France and Canada still champion to help the underdeveloped world become less so.

The Japanese, a summit watcher remarked, will continue "hoping that the concessions they made will keep the others off their backs even if the benefits require a microscope to find."

But, barring unforeseen theatrics, the heads of state, as so often in the past, will mask their innermost feelings during the 23 hours of formal and informal talks next Friday, Saturday and Sunday.

Thus, the most the Versailles gathering may produce is some unfettered discussion, which is what French former president Valery Giscard d'Estaing had in mind when he dreamed up the meetings.

Or, as a summit veteran said, betrayed by his otherwise excellent English, "The summits never do lay eggs."