GERMANY is discovering the downside of open borders in Europe.Thousands of East Europeans, mostly Romanians and Bulgarians, are camping out just beyond Germany's eastern frontier, waiting for a chance to slip into the land of prosperity. It is the scene of a nightly cat-and-mouse game between German border guards and determined illegal migrants who wade from Poland across the Neisse River or scramble over the mountains from Czechoslovakia. Two hundred extra border guards, as well as helicopters and boats, have been sent to the area. But if the migrants know to utter the magic word "asyl" when they are caught, they are sent on to a refugee camp in eastern Germany instead of being delivered back across the border. Germany has one of the most liberal asylum laws in Europe, and the number of asylum seekers here is markedly rising - to the point where many Germans want to hang out the "no vacancy" sign. As German Chancellor Helmut Kohl said in a television interview last Sunday, this is "no land of immigration." He wants to alter the clause in the German Constitution which sanctions the right to seek asylum. He is backed in this by Interior Minister Wolfgang Schauble, who is also pushing a coordinated European approach to the continent's new problem of mass migration. Economic upheaval in Eastern Europe is the driving force behind the wave of asylum requests in Europe, says Mr. Schauble. Political persecution plays only a "marginal" role, he said in a press statement last week. So far this year, according to Schauble, requests for refugee status are up 15 percent in Germany. More than 200,000 asylum seekers are expected by year end. Half of the asylum requests made in Europe last year were filed in Germany. Meanwhile, next to Italy, Germany has the highest number of illegal aliens in Europe, an estimated 400,000, according to the International Labor Organization. Bonn is to begin bilateral talks on the migration issue with Warsaw later this month and with Prague in September. Schauble hopes he can arrange a meeting on the subject in October with leaders from France, Italy, Austria, and Switzerland. The migration problem, he says, is a pan-European one. What's needed, the interior minister suggests, is a harmonization of asylum procedures and criteria within the European Community, as well as aid to Eastern Europe to improve living conditions there. He also wants to see Germany's system of refugee distribution - in which each German state has a quota matched to its estimated ability to absorb refugees - adopted by the EC. The European approach is all well and good, say local politicians in Germany, but their country has an immediate crisis on its hands and needs fast relief. Housing all over Germany is tight. Cities in western Germany say they have no capacity to take in anyone else. Many are still handling east Germans from the last two years, plus ethnic German immigrants from all over Eastern Europe, as well as asylum seekers. The gymnasiums and bomb shelters are full, they say; now it's east Germany's turn. The east German states are bearing the main load of this summer's stream of east European refugees arriving via Poland and Czechoslovakia. But they are not well prepared, logistically or psychologically, to deal with the "brand new problem" of refugees, says Helga Wanke, a spokeswoman for the state of Brandenburg, which borders Poland. Unemployed east Germans fear job competition, and reports of attacks on foreigners in east Germany appear almost daily in the press. The immigration issue will be addressed in September when lawmakers return from vacation. Kohl and Schauble want to retain the right to asylum in the constitution but alter it to allow border officials to turn back asylum seekers immediately if they come from a list of countries where no persecution exists. The list would include the newly freed countries of Eastern Europe, including Romania, although it is still considered by Helsinki Watch to be a violator of human rights. Others want simply to speed up the asylum process, while still others want to institute an immigration quota system. Germany's practice of granting immediate citizenship to East Europeans of German descent (from outside east Germany) is also up for debate, though this is untouchable in Kohl's eyes. Over the last two years, about 775,000 such immigrants arrived here, and although they are not classified as political refugees, they require the same integration services and temporary housing as refugees, and are considered just as much of an administrative burden by local authorities. Ironically, despite all the complaining from local officials trying to integrate newcomers, immigrants are proving to be a necessity for the German economy. The indigenous population here is aging, and the 2.5 million new arrivals of the last two and a half years (east Germans, ethnic Germans, and refugees) have filled a job niche, according to a report by the Institute for the German Economy in Cologne. From this group, about 80 percent of those of working age have so far found jobs - many of them jobs for which no German worker could be found, the report says.