EUROPEANS are pulling out all the stops to try to find a diplomatic solution to the crisis in Yugoslavia.Today, foreign ministers of the European Community will gather for a special session at The Hague to address the crisis. They are expected to discuss an arms embargo and freeze on economic aid to Yugoslavia, as well as the possible recognition of Slovania and Croatia, the two republics that declared independence from Yugoslavia on June 25. These are considered viable options if the recent lull in fighting proves short-lived or the concerned parties refuse to negotiate. The ministers will also review the results of this week's emergency meeting of the Conference on Security and Cooperation in Europe (CSCE) in Prague, which was still meeting at press time yesterday. The CSCE's 35-member nations, which include all the countries of Europe, plus the United States, Canada, and the Soviet Union, called for an immediate end to the fighting and agreed to send an observer mission as soon as possible to Yugoslavia to oversee a cease-fire and return of tanks and armed forces to th eir bases. It was the first-time use of a new power of the CSCE, in which any 13 members can summon, on short notice, high officials from all member states to deal with a crisis. Europeans who want the CSCE to take on more responsibility for security on the continent viewed the Prague meeting as an important test case. The CSCE underwent another first this week when Austria used the CSCE's new Conflict Prevention Center in Vienna to demand information on "unusual" military activity in Yugoslavia. Although the delegates in Vienna also issued a statement supporting a cease-fire, Austrian Foreign Ministry spokesman Walter Greinert said his country was disappointed because the Yugoslav delegation refused to acknowledge that their fighter jets had violated Austrian air space. Austria has a different perspective on Yugoslavia than its European colleagues simply because it shares a border with it. Mr. Greinert says that Europe and the US underestimated the depth of ethnic strife in Yugoslavia and that their show of support for unity, especially in a CSCE statement issued in Berlin two weeks ago, "could be interpreted that the [Yugoslav] Army has a free hand over Slovenia - that it's unity above all else." Given the ethnic strife and separatist movements in the Soviet Union (and in Britain, Spain, and France), it is "understandable" why most countries wanted to prevent Yugoslavia's split-up, says Greinert. But "not everything can be seen globally. There are individual cases," he says. AS the violence heightened this week and it became clear that there is still a solid Communist core in Belgrade, Western Europe and the US moved away from a policy favoring unified Yugoslavia to one that can accept a split if carried out in a peaceful manner. The EC, says a Foreign Office official in Bonn, "is more ready to recognize [Croatia and Slovenia] than it was 14 days ago, but it is not ready to do this yet." First, say the West Europeans, conditions must be created for talks with all sides in Yugoslavia. The Europeans expect to play an active role in creating these conditions by sending observers and possibly mediators. They were encouraged by the recent calm in Yugoslavia, hoping it was the result of enormous international pressure exerted this week. For most of the week, however, Europeans were frustrated by the apparent ineffectiveness of their many diplomatic efforts. Despite all the meetings, calls for cease-fire, and two missions of an EC "troika" of foreign ministers to Yugoslavia, the fighting raged. Political dialogue was having no effect as long as the Yugoslav acted independently from political leaders in Belgrade. But despite the disappointments, the Europeans are not going to give up on diplomacy. Aside from the EC session tomorrow, Italy's foreign minister wants to hold a meeting in Budapest tomorrow with Yugoslavia's immediate neighbors.