BELGRADE, Yugoslavia (AP) _ The forces of Croatia and Slovenia, Yugoslavia's breakaway republics, would be outmanned and outgunned in a war with the federal army.

But structural and personnel problems weaken the federal army's fighting ability. Here are some facts about the federal army and the militias in Croatia and Serbia:

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FEDERAL ARMY - Of the army's 180,000 members, 110,000 are conscripts from all of Yugoslavia's myriad ethnic groups, including Croats and Slovenes. In case of armed conflict, some desertions are likely, mostly by Slovenes, whose sense of belonging to Yugoslavia has traditionally been the weakest.

Most effective in any full battle against Croatia and Slovenia are likely to be soldiers from Serbia and allied Montenegro, the two republics most opposed to the breakup of Yugoslavia. They comprise nearly 50 percent of the conscripts and about two-thirds of the professional force.

The army's effectiveness may also be weakened by confusion about whom to take orders from. The eight-member collective presidency, which commands the army, is paralyzed over a leadership dispute and split on the issue of independence along Serb-Croat lines.

The army has 2,000 tanks, 350-400 combat aircraft, most of them older issue Soviet MiGs, and nearly 150 French-built helicopters, most armed with antitank missiles.

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CROATIAN FORCES - Croatian security forces are reported to number about 70,000 members, some in the newly created National Guard, the rest in the police. Many in the National Guard are police transfers, and there is confusion in the ranks as to whether they are soldiers or policemen.

The Croatians have little armor except for several wheeled armored personnel carrier used by police to control riots. They have no military aircraft.

In their own republic, they are opposed by an estimated 20,000 ethnic Serbs armed with submachine guns and rifles, who would probably be joined by thousands of volunteers from neighboring Serbia in case of conflict.

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SLOVENE FORCES - Slovene authorities claim they can raise an army of 20,000 men, with another 50,000-60,000 in reserve. But Western military attaches in Belgrade say those figures are inflated. The attaches also say that, like the Croats, the Slovenes need years of training before they are professional fighters.

The Slovenes reportedly have some anti-tank missiles but little else that they could use against a massive attack by the Yugoslav People's Army.