ZAGREB, Croatia -- It was a shotgun wedding ordered by the United States that ended the war between Moslems and Croats in Bosnia-Herzegovina, and three months into the marriage there are growing signs that it may not last. Hardline politicians seeking to undermine the Moslem-Croatian reconciliation are overwhelmingly outnumbered by moderates desperate for peace in both Bosnia and Croatia. But President Franjo Tudjman remains resistant to the union with Bosnia, and UN and European mediators are pushing a peace plan that the alliance has doubts about. Additionally, Croatian nationalists appear to be merely tolerating the pact in order to avoid threatened sanctions. Croatian media continue to refer to Bosnian Croat separatists by titles that were abolished by an agreement to create a federation between Bosnian Moslems and Croats. And nationalist supporters of discredited rebel leader Mate Boban remain in their posts, still referring to him as their president and to their proclaimed Republic of Herzeg-Bosna. Rebel patrons in the Croatian leadership here have kept alive the supply lines to the nationalists headquartered in Mostar and continue to coordinate military and political strategy with the supposedly ousted leaders of the rogue Bosnian Croat state. Bosnian Croat forces had been suffering tremendous battlefield losses in the fighting with Moslems before the federation deal was pressed on Zagreb and its proxies in Bosnia. The year-long war waged by Croatian nationalists to secure a Croatian ministate in Bosnia resulted in at least 10,000 deaths and the displacement of as many as 300,000 Croats. U.S. diplomats convinced Tudjman that his country faced devastating economic sanctions unless it stopped backing Bosnian Croat separatism. They also promised reconstruction aid and investment as an inducement if Croats mended fences with Bosnian Moslems. A truce was proclaimed in late February, and an agreement creating a Moslem-Croatian federation in Bosnia was signed March 1. The rapprochement has allowed the civilian populations to restore some sense of normalcy in most areas the two groups share. But Croatian politicians and military leaders regard the federation accord as either a stepping stone to a confederation with Bosnia that would be dominated by Zagreb or a temporary maneuver to deflect the threat of sanctions. When Tudjman paid his long-delayed visit to Sarajevo last week, he professed commitment to the new union and inaugurated a Croatian embassy in the Bosnian capital. But once back on home turf, he pandered to the skeptical right wing by casting the visit as more gesture than genuine allegiance. "This federation agreement was signed under pressure," said Croatian parliamentary leader Josip Manolic, who recently broke with Tudjman's ruling Croatian Democratic Union, the HDZ, in protest of its Bosnian policy. "Some people still want to see the Washington agreement put into force, but a large segment of those in the HDZ are the ones who promoted the war option with the Moslems in the first place and they are undermining the agreement," Manolic warned. A joint Moslem-Croatian army has been proclaimed by the new federal leaders of Bosnia, but there has been little if any evidence so far of cooperation on the ground. Bosnia's Moslem-led government army has fanned out across a broad and strategic arc of frontline in the northeast of the republic. The troops are reported to be preparing for a series of offensives aimed at wearing down the already demoralized Serbian rebels, who have a huge advantage in heavy weapons but too few soldiers to hold the territory they have conquered. The Bosnian Croat forces have lately allowed the government unhindered passage through areas they command in central Bosnia, and the halt in Croatian-Moslem fighting has freed troops for the move against Serbs. But political and military observers here note that the Bosnian Croat units in the nationalist heartland of Herzegovina have not lifted a finger to help their reputed allies wage the campaign for liberation. On the contrary, they have sought to undermine the government offensive by stirring up fears among Bosnian Croats that their communities would be at risk of Serbian reprisals if they back Moslems. A mosque was blown up in the tense town of Vitez late last month, and UN troops have reported renewed fighting in one of the deadliest flash points of the Moslem-Croatian war, Gornji Vakuf.