IN opening an international conference this weekend on the crisis in Yugoslavia, the European Community faces tests that go beyond the stated goal of settling the territorial claims tearing apart the country.That goal will be difficult enough in itself. Despite the EC-sponsored agreement signed Sept. 2 by all six Yugoslav republics to a cease-fire and a commitment to settle border disputes through negotiation, the war in the Republic of Croatia has only worsened this week. Serbian guerrillas, backed by the Serb-dominated Yugoslav federal Army, reportedly gained control of nearly a quarter of the republic's eastern section, where much of Croatia's 12 percent Serb minority lives. The death toll in more than two months of fighting is approaching 400. For the European Community, the stakes in the Yugoslav crisis are particularly high. Despite the fact that they have the backing of the 35-member Conference on Security and Cooperation in Europe (CSCE), the EC will be trying to resolve virtually on its own an explosive international crisis. The conference, set to begin Saturday at The Hague, will also provide a test of political cooperation among the EC's 12 members. EC officials openly wonder if their own negotiations toward a tighter political union will be stalled by the Yugoslav distraction, or goaded on by a deepening realization of the international role that will be expected of the EC in the future. EC Commission President Jacques Delors in recent weeks has taken to describing the Community facing the Yugolslav crisis as "an adolescent taking on an adult problem." For Mr. Delors, the EC needs new rules so that it can work more quickly, at deeper levels of cooperation. Others favor a go-slow response on political integration, emphasizing what the Community has accomplished under its current system. As one British official says, "Given the very difficult circumstances of a civil war, the 12 have performed quite well, and that suggests to us that the Community's system of foreign policy cooperation works sufficiently as it is right now." Germany, on the other hand, is clearly impatient with the amount of time it has taken the EC to work out unanimous positions (as it must under current rules) for action on Yugoslavia. The EC has been meeting regularly on the crisis since late June. German Foreign Minister Hans-Dietrich Genscher has called for majority decision-making to speed up Community action. German Chancellor Helmut Kohl told the parliament on Wednesday that "If dialogue and peaceful coexistence are no longer possible," then Germany will move to recognize the breakaway republics of Slovenia and Croatia. Yet recognizing the two breakaway republics presents special problems for Germany, which may be why top aides to Mr. Genscher are said to be recommending against independent German action. Germany likes to act as an advocate of strong common EC action. Moving on its own on Yugoslavia could hurt its blooming influence within the EC. In addition, recognition would raise questions about similar issues facing a disintegrating Soviet Union. Just this week Mr. Kohl said the Soviet republics must retain a common foreign policy, military, and economy as the basis of a "renewed Soviet Union." Recognition now would send the wrong message, says one Western diplomat in Bonn. It would clearly "have a damaging effect on the current affairs in the Soviet Union," he says. The French, the Dutch, the British, and the Spanish remain opposed to recognition, although French sources believe French President Francois Mitterrand may be shifting his view after a meeting last week with Croatian President Franjo Tudjman and as intense fighting has continued.