A DEBATE is developing between Britain's Prime Minister Margaret Thatcher and the president of the European Commission over the future size and shape of Europe. Mrs. Thatcher is determined to ensure that the 12-member European Community (EC) expands after 1992, taking in East European countries that free themselves from communism, as well as some neutral European states.
But EC Commission President Jacques Delors is adamant that the Community should be kept as small as possible for as long as possible.
During a visit to Czechoslovakia, Hungary, and Switzerland at the end of last month, Mrs. Thatcher applied pressure for the EC's early enlargement. In Prague, she encouraged President Vaclav Havel by saying that soon after 1992, Czechoslovakia would be able to join.
In Budapest, she had a similar message for Hungarian Prime Minister Jozef Antall, whom she congratulated for leading ``Eastern Europe's only conservative government.'' In Zurich, she said Swiss neutrality ought not be an obstacle.
In Brussels, an official said that Mr. Delors was ``concerned'' by Thatcher's approach. Delors often has said that the Community should consolidate itself before taking additional members aboard. In June, he argued that the EC should sign trade agreements with the members of Comecon, the Moscow-led trade grouping, and with the European Free Trade Association, a Western free-trade grouping that includes Austria, Switzerland, Sweden, Finland, Iceland, and Norway.
His plan includes ``three concentric circles,'' with a virtually unchanged EC at its heart, and the other countries enjoying economic but not political ties with it.
It is this conception that Thatcher opposes. Since becoming prime minister 11 years ago, she has argued against the political and economic integration of the EC. Speeches in the last two years have made it plain she opposes a federal arrangement that might lead to a ``United States of Europe.''
In Prague, she spelled out her vision: All European countries that wish to join the EC should be offered first-class membership. Although Delors and his supporters are convinced that Europe should become deeper before it becomes broader, Thatcher favors enlarging the group as a way of preventing its domination by Europe's strongest countries, such as West Germany.
The pace of events may be on Thatcher's side.
Austria has already applied to join the EC after 1992, as have Turkey, Malta, and Cyprus. Thatcher's support for Swiss membership reflects her view that it would make little sense to have Austria in the EC without Switzerland. The same applies to Hungary, which has close ties with Austria. She is also believed to favor EC membership for Sweden, Norway, and Poland.
Thatcher has chosen a volatile time to spread her message. EC members' uneven response to the Gulf crisis has shown them to be far from a homogeneous force.
The economic impact of the crisis has also been a shock. Earlier, all but two or three EC members were keen to move toward monetary union in January 1993. But early in September, at a majority of the finance ministers meeting in Rome were having second thoughts.