Across a U.N.-patrolled buffer zone, Serbs and Croats eye each other suspiciously in the Krajina region. What will happen if the peacekeepers start withdrawing?

......."If the Croats want war, they'll get war," said a Serbian corporal,....."but this time we'll do properly".

Across a buffer zone monitored by the U.N. troops, though, the Croatian governement is ready to gamble that such words are mere bravado. "There's such an overexaggeration of the military power of the Serbian forces," said Zoran Bosnjak, an adviser to Croatia's foreign minister. "It's just incredible the way it's exaggerated." Talk like that, on both sides of the front line, has the world worried.

The Croatian government is determined to follow through on its promise to order 12,000 U.N. troops to begin moving out by the end of March from the zone between the Croatian hearthland and the mountainous one-third of its territory still held by rebel Serbs. If the U.N. troops leave, military analysts figure, both sides will rush to seize mountaintops, river crossing and other strategic point in the 1.2-mile-wide, U.N.-held zone. Weapons caches now under U.N. guard will be opened.

......."The U.N. has been preserving a negative status quo," said Bosnjak, the Croatian Foreign Ministry official. "And we have to change some of the basic ingredients in this former Yugoslavian brew".

......."This country of ours was difficult to create," said Milos Vucinic, secretary of the City Council here. "And now we're supposed to give it up to become second class citizens in Croatia."

......A possible solution to the conflict was offered a few weeks ago in an initiative led by the U.S. and Russian ambassadors to Croatia. They drew up an autonomy plan that would allow the Krajina region substantial independence within Croatia, giving the Serbs here the ability to raise taxes and their own flag, among other things. The Croatian government accepted the plan as a basis for negotiations. But the Krajina Serbs refused to even look at it, demanding instead that the United Nations first agree to not withdraw. Now the Krajina Serbs are mobilizing for war. New trenches are being dug. Rifles are being cleaned. And reserve soldiers must have permission from their commanders to leave their towns. If there is a war, it will be much different from the 1991 war, analysts say. The Croatian government, whose army outmans the Krajina Serb army 2 to 1, has had three years to build up its arms. The rebels, though, remain well armed, and they recently signed a military cooperatio agreement with the strong rebe

l army of Bosnian Serbs, formalizing a the facto alliance.

Most analysts think the Croatian government is overstimating its military strength, though they aknowledge that government forcescould win back at least some of the Krajina. The price in lives on both sides would be high, and Zagreb might even be the target of some shelling. But recent public opinion polls suggest that the Croatian people support their president, Franco Tudjman, and are willing to run the risk of war.

......Meanwhile, U.N. officials in this part of the Krajina are nervously watching the Serbian military buildup.

......The United Nations hasn't always felt welcome here, of course. In the last two months, armed gangs have stolen 30 U.N. vehicles. The cars and trucks were repainted and driven around the region's small villages, obvious to everyone except, of course, the local police. The police started to act on U.N. complaints only when it appeared the forces might be leaving. "It's funny how things have changed," said James Kanu, the U.N. spokesman in Topusko, about 30 miles east of here. "A few weeks ago the people in the Krajina were saying we were useless. Now they're saying. 'Don't go.'"