BELGRADE, Yugoslavia -- The Serb-dominated federal army Friday extended military service for conscripts and reservists in apparent anticipation of extended hostilites despite a joint appeal by the United States, Soviet Union and the European Community for the immediate implementation of a cease-fire.
Sporadic fighting, meanwhile, flared without respite in contested areas of independence-seeking Croatia, pitting Croatian forces against federal troops and rebels of its Serbian minority backed by the rival communist-ruled Serbian Republic.
U.S., Soviet and EC envoys on Thursday evening presented a joint appeal to the leaders of Serbia and Croatia, and the communist Serbian federal military command for an 'immediate and complete' cease-fire under a Nov. 23 truce accord brokered by U.N. special envoy Cyrus Vance.
The move came after the U.N. Security Council endorsed Vance's recommendation against the dispatch of a peace-keeping contingent to Yugoslavia because of the failure by the warring factions to fully implemented the 14th truce agreement of the five-month-old civil war.
The appeal was delivered to Yugoslav Deputy Defense Minister Stane Brovet and communist Serbian President Slobodan Milosevic in Belgrade by the U.S. and Soviet ambassadors and by the charge d'affairs of The Netherlands, the current chairman of the 12-nation EC, the Tanjug news agency reported.
The U.S. and Soviet consuls general in the Croatian capital of Zagreb handed the appeal to Croatian nationalist President Franjo Tudjman, Tanjug said.
In Belgrade, the federal Defense Ministry said that in line with an order of the four-man pro-Serbia bloc that seized control of the Yugoslav collective head of state, it was adding three months to the compulsory 11-month term served by conscripts.
Reservists, who generally serve 45 days, will have to remain in the army for four months, the ministry said.
The defense ministry said that the army 'in conditions of direct war danger ... is carrying out tasks of vital significance for the defense against onrushing (Croatian) fascism and to prevent the spreading of the civil war and genocide against the Serbian population in Croatia.'
It said the order was to ensure adequate levels of personnel and combat readiness 'as a general mobilization has not been declared.'
Western diplomats said the service extensions reflected the military's anticipation of prolonged hostilities.
'The army ... in their hearts of hearts ... consider the likelihood of continued war in Yugoslavia, something which can't be stopped,' said one.
Western diplomats said the decision was fresh evidence of serious manpower shortages within the army, which has drained along ethnic lines and has been plagued by desertions, flights abroad by draft-age men, refusals by more than 10,000 Serbs to report for service, and disenchantment among reservists unsure of why they are fighting.
'They are obviously having a lot of trouble with reservists,' said a Western diplomat. He noted that about 1,000 reservists staged a raucous protest in the Serbian town of Kraljevo on Thursday against orders to report for a second term of military service.
In addition, about 200 reservists angered by a lack of replacements abandoned their positions Thursday night near the eastern town of Vukovar, which fell to Serbian forces on Nov. 18, and returned to their homes in the Serbian town of Kraguljevac, the national newspaper Borba reported.
On the battle front, Croatian units fought artillery and infantry clashes with Serbian forces around the central Nova Gradiska area, Tanjug quoted military sources as saying. It gave no casualty figures.
Tank, artillery and infantry duels also flared around the Croatian stronghold of Vinkovci, a major road and railway junction in the eastern Slavonija region, 100 miles northwest of Belgrade.
Croatian state-run Zagreb Radio said Serbian forces opened fire on Vinkovci from the village of Mirkovci. The federal army claimed Croatian militiamen struck first.
Ed Koestal, a spokesman for the EC monitoring mission in Zagreb, said that EC observer teams were working to mediate a cease-fire in the chief Slavonija town of Osijek, which has been repeatedly bombarded by encroaching Serbian forces for almost a month.
EC teams were also attempting to broker a truce around the combat- ravaged central town of Pakrac, he added.
Croatian and Serbian forces, meanwhile, exchanged mortar fire at Stankovci, north of Croatia's central Adriatic coastal town of Sibenik, Tanjug said.
The war ignited by Croatia's June 25 independence declaration has left thousands of people dead and forced more than 500,000 Serbs and Croats to flee battle zones amid widespread destruction and damage to villages and towns.
Croatia's 580,000 Serbs -- about 12 percent the breakaway republic's population -- rebelled against the Croatian regime fearing persecution in an independent state.
Serbia, which contends it is not at war with Croatia, claims all of Yugoslavia's 8.3 million Serbs should reside in a single state if the six-republic federation ruptures. The federal army says it is protecting Croatia's Serbs from the republic's 'fascist' regime.
Croatia charges that Serbia, supported by the federal army, is seeking to annex its Serbian enclaves for inclusion in a 'Greater Serbia' or rump Yugoslavia.