Updated

Serbian and Croatian officials on Thursday sought to defuse tensions that soared after a Serb far-right leader burned a Croatian flag while defying orders to return to a U.N. war crimes tribunal.

After Vojislav Seselj set the Croatian flag on fire on Wednesday in Belgrade, Croatia recalled its ambassador to Zagreb for consultations and nationalist politicians in both countries exchanged harsh words. It triggered the worst political crisis since the two former Balkan foes fought in the 1990s wars.

Croatian Foreign Minister Vesna Pusic said Thursday that "Croatia wants to calm down passions" and "focus on the future, economic, political and security."

Her Serbian counterpart Ivica Dacic said that "the strengthening of trust between the two states must not be jeopardized by inappropriate rhetoric of individuals."

Relations between Serbia and Croatia are crucial for the stability in the Balkans which is still reeling from the bloody breakup of former Yugoslavia. Serbia needs support from EU-member Croatia in its effort to join the 28-nation bloc.

Judges at the U.N. tribunal in The Hague, ruled Monday that Seselj had breached conditions of his provisional release on health grounds, and ordered him to return to its cellblock. Among other charges, Seselj is accused of recruiting notorious Serb paramilitary forces during the wars in Croatia and Bosnia.

He has refused to go back voluntarily after spending 12 years in custody in The Hague for his long-running trial.

Croatia has demanded that Seselj be sent back to custody after his frequent nationalist outburst against Croatia, including saying in an interview he would go to the neighboring country "only on a tank and fully armed."

"I can't wait for the European Union to abort talks with Serbia over my behavior," Seselj said Thursday. "It is my goal that Serbia should never become a member of the European Union."

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Associated Press writer Jovana Gec contributed.