GENEVA (AP) _ The Common Market and the Soviet-led COMECON, Europe's main trading blocs, opened talks today in Geneva that delegates say could eventually lead to formal relations and closer cooperation.

Common Market spokesman Anton Leicht said delegates began the three-day talks this afternoon at the International Labor Organization building here, which was chosen as a neutral meeting site.

The talks are exploratory in nature, being held between technical experts, not senior officials, he said.

John Maslen, head of the Common Market delegation, said in an interview last week that the meeting is not expected to produce substantial agreements, but could lead to a joint declaration this year formally establishing relations and pledging closer cooperation between the two groups.

Both groups were founded after World War II to promote trade and economic ties among their members.

The 10 COMECON members are among the small number of nations that have not established relations with the Common Market, which the Soviet Union called an imperialist tool when it was formed.

The talks represent a re-establishment of a dialogue that was broken off in 1981 after five years of unsuccessful negotiations.

Members of COMECON, or the Council for Mutual Economic Assistance, are the Soviet Union, East Germany, Hungary, Romania, Bulgaria, Poland, Czechoslovakia, Mongolia, Vietnam and Cuba.

The Common Market, formally called the European Economic Community, or EEC, comprises Britain, West Germany, Italy, France, Denmark, Spain, Portugal, Greece, Belgium, Ireland, Luxembourg and the Netherlands.

Common Market officials have said the East bloc's renewed interest in relations reflects Soviet leader Mikhail S. Gorbachev's desire to widen Moscow's access to hard currency and Western technology.

Moscow has also made overtures to China, member nations of the Oorganization of Petroleum Exporting Countries countries and GATT, the 92- nation General Agreement on Tariffs and Trade, in an apparent effort to broaden economic ties with the outside world.

Three-quarters of all Soviet exports to Western nations last year went to Common Market nations, statistics show.

Total trade between the Common Market and European members of COMECON was $43.9 billion last year, down four percent from 1984.

Common Market officials have insisted that any formal agreement with COMECON not include trade on a bloc-to-bloc basis. They say COMECON, unlike the EEC, has no responsibility for its members' trade policies, and that is has no common tariff or commercial policy.

Common Market officials also are wary of the political aspects of an accord with COMECON that would appear to indicate they condone the separation of Europe.