Serbian-Led Army Pounds Croatian Ports, Threatens to Shell Fortress : Yugoslavia: European negotiators again claim to have worked out a cease-fire.

The Serbian-led federal army pounded strategic Croatian ports along the Adriatic Sea on Friday and threatened to bombard the historic walls of Dubrovnik if Croatian fighters take refuge in the medieval seaside fortress.

The assault on coastal resorts that used to generate billions in tourist revenue for Croatia appeared aimed at damaging those areas of the war-ravaged republic to which rival Serbia has no historic or ethnic claim.

As fighting intensified, European mediators who met in the Netherlands again claimed to have worked out a cease-fire in the bitter conflict between Yugoslavia’s largest republics.

Federal forces have executed a full-scale attack against Croatia this week, seizing land far beyond the Serbian-populated villages that they were ostensibly seeking to protect from Croatian national guardsmen.

The army’s advance to within 20 miles of the Croatian capital of Zagreb and its mortar barrages throughout the republic heightened speculation that the pro-Serbian forces were expanding their land-grab to have bargaining chips to trade for Serbian-inhabited territory in future peace negotiations.

Serbian and federal troops have conquered about one-third of Croatia since it declared independence along with Slovenia three months ago. No official death toll from the fighting has been released, but as many as 1,000 are believed to have been killed.

Serbia and its three allies on the eight-man collective federal presidency ordered an expanded military mobilization Friday, the Tanjug news agency reported.

Four of the presidential delegates--those from Croatia, Slovenia, Bosnia-Herzegovina and Macedonia--boycotted the session because they considered it illegal. Only the federal president, Croatia’s Stipe Mesic, is empowered to convene sessions of the ruling body that commands the armed forces.

Mesic on Thursday accused the four pro-Serbian members of staging a coup d’etat by issuing military orders in the name of the entire presidency while meeting without a quorum.

No details of the mobilization were given, but the federal forces have suffered numerous desertions and heavy casualties in the latest offensive.

On Friday, air force jets strafed Croatian television’s transmission tower in a Zagreb suburb, but broadcasting was knocked out for only a few minutes.

Croatian radio reported that federal bombers attacked the Cilipi airport near Dubrovnik, navy gunboats shelled the marina resort town of Slano a few miles to the north and air force attack planes destroyed a bridge that cut off the last open road to the port of Zadar.

Hundreds of women and children were forced to flee their homes, and forest fires blazed in the wooded hills above Dubrovnik, Croatian media reported.

An army statement carried by Tanjug accused Croatian forces of retreating behind the medieval fortifications that ring Dubrovnik and “holding it hostage together with all of its people.”

While the army said it would “do everything to spare Dubrovnik, a city of infinite historical and cultural value,” it made clear that military considerations would be put ahead of concern for historical treasures.

The Croatian Defense Ministry in Zagreb denied its forces were taking refuge in the city.

A Serbian reservist in Belgrade, who spoke on condition of anonymity, speculated that the federal forces were intent on flushing out all Croatian fighters from Dubrovnik because of its proximity to naval bases near Tivat, an Adriatic port in Montenegro, Serbia’s lone Communist ally.

Dubrovnik, the pride of Yugoslavia’s tourism industry, is located along a narrow band of Croatian territory hemmed in by Bosnia and Montenegro. Because the lucrative resort was an independent city-state for 500 years before Yugoslavia was formed, it has long been a source of irritation to Serbs that Dubrovnik was made part of Croatia. Federal forces encircled Dubrovnik earlier this week, cutting off communications, power and water.

Tanjug reported that navy gunboats reinforced a blockade of seven ports and that renewed artillery and mortar battles broke out in the eastern Croatian cities of Vukovar, Osijek and Vinkovci.

The stepped-up army assaults Friday came as leaders of the European Community persevered with a so-far fruitless attempt to end the fighting in Yugoslavia through negotiation.

Dutch Foreign Minister Hans van den Broek, whose country now heads the 12-nation EC, summoned federal authorities and the Croatian and Serbian presidents for emergency talks in The Hague. After a two-hour session, Yugoslav Defense Minister Veljko Kadijevic announced that he had agreed to halt the air, land and sea offensive against Croatia if republic forces lift a blockade of federal bases.

By shutting off food and power supplies to army garrisons in the republic, Croatian forces succeeded in provoking mass desertions from the federal army, triggering this week’s offensive.

Although Croatian President Franjo Tudjman told reporters that he had ordered a pullback from the garrisons and Serbian President Slobodan Milosevic declared himself “much more optimistic,” six previous cease-fires have been broken, usually within hours of their announcement.

Croatian Information Minister Branko Salaj said the success of the latest EC-brokered truce would depend on the army. He warned that some renegade units have repeatedly acted in defiance of the military leadership’s orders to hold their fire.

Despite tireless effort, the EC diplomats have been unable to make any headway in resolving the complex ethnic issue at the core of the Yugoslav conflict. Serbia insists on independence for those areas of Croatia where Serbs are a majority, while Croatia denies its largest minority is discriminated against and accuses Serbia of blatant territorial expansion.

About 600,000 Serbs live in Croatia, Yugoslavia’s second-largest republic with 5 million people. But less than a third of the Serbs live together in towns and villages where they are the majority, with the rest scattered broadly across the arrow-shaped republic that stretches from the Adriatic to the border with Hungary.

When Croatia declared independence June 25, ethnic Serbs in the republic--backed by guerrillas from Serbia and the federal army whose officers corps is 70% Serbian--began attacking Croatian police and militia units. Some Serbs assert that they were responding to attacks on them by Croatian nationalists; others say they moved first out of fear of such ethnic persecution.

Federal land and air forces first attacked Slovenia, the smallest but most prosperous of the six Yugoslav republics. But after the federal troops were humiliated by the poorly armed but well-organized Slovenian defenders, the army retreated from the republic and Serbia agreed to an EC-brokered deal on July 8 that put a three-month hold on Slovenian and Croatian independence--a condition that expires Monday.

Serbia’s orchestrated push to gain more Croatian territory gives the dominant Yugoslav republic more to negotiate with in redrawing the boundaries of Croatia in return for a lasting peace that would allow foreign countries to recognize Slovenia and Croatia as sovereign nations.