THE number of Western countries setting up diplomatic relations with the Baltic republics is snowballing."We hope that by the close of business [today], all the members of the European Community (EC) will have established diplomatic relations" with Lithuania, Latvia, and Estonia, says a Foreign Ministry official in Denmark. The Danes, yesterday, sent an ambassador to the Baltics - the first from a Western country. In Brussels today, EC foreign ministers will discuss establishing diplomatic relations with the Baltic states. They will also consider EC associate membership for the Baltics and EC foreign policy as more Soviet republics declare their independence. "The whole world of countries must newly shape its relations to the Soviet Union because it is obvious that a series of republics are seeking independence," said German Foreign Minister Hans-Dietrich Genscher in a radio interview yesterday. The Ukraine and Byelorussia both declared independence over the weekend, and Moldavia's legislature will debate the subject today. Germany and Denmark are both pushing for EC associate status for the Baltics. Similar agreements are being negotiated with Poland, Czechoslovakia, and Hungary, but these talks have dragged because EC members are reluctant to open up their markets to East European agricultural and textile exports. But economists say the Baltics should not, in the near term, threaten the West European market - they are not export oriented and they are not mass producers of agriculture. So it may not be as difficult to get the Community into high gear on associate status for the Baltics as it has been for Eastern Europe. The European Commission, meanwhile, released a study yesterday saying the Baltics would need $3 billion in short-term economic aid. Most Western countries never legally accepted the 1940 Soviet annexation of the three republics, which was based on a secret pact between Hitler and Stalin in 1939. The West maintains that the Baltics are a unique case, and that starting up diplomatic relations with them does not necessitate the same for other Soviet republics, or, even further afield, for Slovenia and Croatia in strife-torn Yugoslavia - which will also be on today's EC agenda. Generally, Europe is inclined to build ties on the republic level without undercutting ties with the central government in Moscow. It was fear of endangering those relations that held many countries back from official recognition of the Baltics last week, even though the three had declared their independence and banned the Communist Party, says Roland Freudenstein, a Soviet specialist with the German Society for Foreign Affairs in Bonn. The turning point, says Mr. Freudenstein, was when Boris Yeltsin, as president of Russia, extended recognition to the Baltic states on Saturday. That amounted to official sanction from the most popular and powerful politician in the Soviet Union, and a guarantee that outstanding issues, such as military and economic relations between Russia and the Baltics, would be resolved.