US Secretary of State Colin Powell said today that Croat hardliners threatened to return Bosnia to the law of the jungle and ruin the progress the country had made since its inter-ethnic war ended in 1995.
Earlier in the Macedonian capital Skopje Mr Powell, on his first trip to the Balkans, urged Kosovo Albanian leaders to do more to prevent new violence in Macedonia if they wanted to retain international backing.
The United States is very proud to have helped end a terrible war, Mr Powell told reporters in Sarajevo after meeting political leaders of the Muslim-Croat federation and Serb republic formed under US-mediated peace accords at Dayton, Ohio.
However we are concerned at the recent reappearance in the country of extremist elements like those that caused so much destruction and misery some years ago, he added.
The challenge to the elected governments here from hardliners in the HDZ (Croatian Democratic Union) party threatens to set back the progress that Bosnia-Herzegovina has made in recent years, he said.
Shortly after he spoke the government of Bosnia's Muslim-Croat Federation urged international peacekeepers to take control of Bosnian Croat barracks, some of which have been occupied by nationalist groups seeking Croat self-rule.
It said any soldiers or police not wearing official insignia would henceforth be considered paramilitary forces and expressed concern that not all weapons and equipment belonging to the Croat contingent were under government control.
Mr Powell said the Croat hardliners in the party who want to pull away from the federation were using nationalist propaganda to preserve their own wealth.
We know full well that the overwhelming majority in this country, Bosnian Croats and others, does not want a return to conflict nor a return to the law of the jungle, he said.
In Macedonia, which has been rocked by months of violence between government troops and ethnic Albanian rebels, Mr Powell met moderate Kosovo Albanian leader Ibrahim Rugova and Hashim Thaci, former commander of the Kosovo Liberation Army (KLA) that fought the forces of then Yugoslav President Slobodan Milosevic.
The Macedonian governments says the rebels are separatist extremists from Kosovo. The rebels themselves say they are fighting for more rights for ethnic Albanians, one third of Macedonia's population.
"We call on Kosovars to join us in denouncing and isolating extremists whose actions are eroding international support for Kosovo and sympathy for its people", Mr Powell told a news conference in Skopje.
US officials said low cloud and bad weather had prompted Mr Powell not to make the 55-minute helicopter ride to the Kosovo capital, Pristina. They did not cite security considerations.