As Partition Looks Nearer, Bosnian Muslims Are on March : Balkans: Sarajevo is reported calm. But government actions elsewhere fuel skepticism about latest cease-fire.

As Bosnian leaders debated how to carve up their war-ravaged land, government troops captured two Croat-held villages Saturday in a desperate race to occupy territory before the new map can be drawn.

The twin settlements in central Bosnia-Herzegovina, Kruba and Bistrica, fell less than 24 hours after Muslim, Serbian and Croatian leaders meeting in Geneva announced a tentative agreement to end Bosnia’s 16-month civil war.

Today, military chiefs of the factions are to meet in Sarajevo, Bosnia’s artillery-blasted capital, to debate how to deploy U.N. peacekeepers to monitor compliance with the cease-fire they agreed to Friday.

But fears were rife that Muslims, the biggest losers of territory in the war, might not do the bidding of their political masters--particularly since over the past two months it is the Muslims who have scored a series of battlefield victories.

Mixed news Saturday from Bosnia fueled skepticism that peace might finally be at hand. The guns around Sarajevo were reported to have fallen eerily silent, but despite the cease-fire, Muslims were said to be continuing the southward advance they began in central Bosnia in June.

As night fell, U.N. forces were also gearing for what they feared could be a major outbreak of hostilities between Croats and Serbs in southern Croatia.

Under the terms of a bilateral agreement, Croatia’s armed forces were supposed to relinquish control of a strategic pontoon bridge almost 900 feet long linking the republic’s interior with the Adriatic Sea.

The span at Maslenica, reopened with great pomp two weeks ago by President Franjo Tudjman, was supposed to be placed in the hands of U.N. forces by midnight Saturday. Without that proviso, Serbian gunners would almost certainly have bombarded the bridge long ago.

The U.N. commander in the former Yugoslav republics, French Gen. Jean Cot, made a reconnoitering mission to Maslenica and its environs during the day. With the midnight deadline 2 1/2 hours away, Cot told correspondents in Zagreb that he was going to meet for last-minute talks with a Croatian delegation.

If the Serbs maintain their demand that the accord be respected and the Croats refuse to pull back, Cot said the 2,000 U.N. troops that he has deployed in the area can do little.

In Bosnia, troops loyal to the Muslim-controlled government poured intense tank and artillery fire into Kruba and Bistrica, which guard a vital mountain road used to truck relief supplies from the Adriatic coast to the Bosnian interior.

The British U.N. forces’ company base in Gornji Vakuf is just a few miles from the villages occupied by the Muslims. “This is the heaviest fighting British forces have witnessed in south-central Bosnia,” a U.N. source told Reuters news agency.

Ethnic Serbs and Croats control virtually all of the former Yugoslav republic of Bosnia-Herzegovina as a result of the civil warfare that has left up to 200,000 people dead or missing. Outgunned on the field as well as diplomatically, Bosnia’s government has agreed only reluctantly to the notion of partition.

In Geneva, European Community mediator Lord Owen gave an idea of the Muslims’ despair by saying the new territorial split needs to provide adequate space to house some 2 million Muslims forced to leave their homes due to war or “ethnic cleansing.”

Sarajevo’s relative calm gave rise to guarded hope that this time, the cease-fire could succeed.

“The indications are that the fighting has abated considerably throughout Bosnia,” Cmdr. Barry Frewer, a spokesman for the U.N. peacekeeping force, told reporters in Sarajevo. But he added, “I say that very cautiously.”

In other developments, the whereabouts of hundreds of Bosnian refugees detained late last week in Croatia remained murky. Fatima Bunguric of the Bosnian Embassy in Zagreb said that as of lunchtime Saturday, three busloads had been moved to the border at Imotski.

The Croatian government announced Friday that it had detained 490 Bosnians who, it asserted, were criminals. But Bunguric said Bosnian authorities have learned that the detainees include four minors, a handful of elderly people and one epileptic--facts that cast doubt on the Zagreb government’s claim.