An effective overall plan by the United States and its allies for curbing strategic trade with the Soviet Union is still far from ready -- and may never be -- despite President Reagan's assertion last weekend that "substantial agreement" on such an approach had been reached.

France's refusal to go along with Reagan's description of the allied consensus, which the president coupled with the lifting of sanctions on suppliers of U.S.-licensed equipment for the Soviet natural gas pipeline, is only the most visible sign of the divisions that still exist on trade with the Kremlin.

According to officials here and in other European capitals, the differences are not over the potential benefits to the West of a coordinated stance on the flow of such items as high-technology equipment or subsidized credits to the Soviet Bloc. The broad outlines of a politically motivated approach to limit Soviet "advantages" in trade were agreed on in alliance summit meetings at Ottawa in 1981 and Versailles in 1982.

Yet the United States' partners recoiled from adopting measures that could be considered "economic war" against the Soviets, and as a group they continue to do so.

The problem now -- after weeks of official meetings in Washington aimed at preventing a recurrence of a serious and damaging breach like the pipeline dispute -- is that the mechanics of controlling trade policies in Western countries are as complex as they were before. The Reagan administration today remains more intent on reducing strategic trade with the Soviets than the allies are and therefore demands far more restrictive terms when specific issues are discussed.

One major new political element does exist, however, that could have a positive impact on the trade question. The accession of Yuri Andropov to the Soviet Communist Party leadership raises the possibility, senior British officials say, of an easing in the atmosphere of East-West tensions that would also lessen U.S. pressure on its allies for tougher trade restrictions.

But that, they concede, is only a dim hope given that the underlying positions of the U.S. and Soviet governments remain unchanged on defense spending, nuclear armament and a host of other issues that are sources of friction.

As it stands, the United States, Britain, West Germany, Italy, Canada, Japan, a representative of the European Community and France (in spite of its anger at Reagan), have essentially agreed to take detailed new looks at four areas of trade -- technology transfer, credits, energy and agricultural exports.

By no means certain is what form those reexaminations would take and what power their results would have. Lord Cockfield, Britain's trade secretary, said yesterday that the studies would best be referred to such existing groups as the Paris-based Coordinating Committee for Export Controls (known as Cocom), or the Organization for Economic Cooperation and Development (OECD), both made up of the industrialized democracies.

A study on alternative energy sources to those offered by the Soviet Union could be prepared by the International Energy Association, according to other British sources. In the meantime, the United States hopes that the allies will make no new commitments to Soviet gas or oil contracts, but the effectiveness of even this point remains to be proven.

For the moment, the clearest test of whether a more restrictive policy can be applied is in Cocom, where a regular four-year review of the list of banned items of potential military use to the Soviets has just begun. It is already clear that there are innumerable differences between the United States and its allies in the group (the members of NATO, except for Iceland and Spain, and Japan).

Cocom, which operates in a corner of the U.S. Embassy compound in Paris with a small staff of about 14 and a budget of around $500,000, would be expanded and its authority substantially enhanced, under an American proposal. Instead of trade specialists and diplomats, the United States favors giving military representatives primary responsibility at Cocom.

Moreover, the United States, sources said, wants to broaden the definition of what might be put to military use and all but eliminate the exemptions for specific contracts which member countries -- including the United States -- now get by the hundreds each year. The Europeans, particularly the French, counter that proposed American definitions are so extensive that virtually all manufactured goods would contain some prohibited items.

Advanced technology in the electronic and computer fields poses problems, but so apparently does such relatively old-fashioned equipment as parts for trucks or dry docks. "Deciding what is obviously commercial or obviously military is a devil of a job," said one trade expert, "especially since many things fall into a gray area."

The review will take a year to complete and should add additional items to the list of proscribed goods. However, the American view, as expressed here and elsewhere in Europe recently by Assistant Defense Secretary Richard Perle, leaves no doubt that a considerable gap exists. So much technology and production equipment has been sold to the Soviets, Perle was quoted as saying, that "in Zelenograd, Russia's Silicon Valley, virtually everything comes from the West."

Credits to the Soviets apparently represent less of a problem. Last spring, under American pressure, the 24 members of OECD took action to lift the minimum interest on export credits to the Soviets to more than 12 percent, bringing them in line with their rates to other major borrowers.

In any case, substantially less credit has been extended to the Soviet Bloc countries this year because of the general wariness of banks to add to the already enormous Eastern European debt. So far in 1982, according to the Financial Times, "Eurocredits" are running at a third of last year's pace. But if economic conditions were to change, officials here believe that competition for Soviet loans might well again override American political objections.

Preparations for studies on energy dependence and agricultural exports envisioned in the Washington meetings are at a very early stage, officials here say. Devising a program for oil and gas purchases outside the Soviet Bloc well into the 21st century or proposing restraints on American grain sales are major hurdles toward a common trade strategy that the alliance is only beginning to face, let alone overcome.