Dissatisfied with the Pope's decision, Kaloyan sent a new letter to Rome, asking Innocent to send cardinals who could crown him emperor. He also informed the Pope that Emeric of Hungary had seized five Bulgarian bishoprics, asking Innocent to arbitrate in the dispute and determine the boundary between Bulgaria and Hungary. In the letter, he styled himself the "Emperor of the Bulgarians". The Pope did not accept Kaloyan's claim to an imperial crown, but dispatched Cardinal Leo Brancaleoni to Bulgaria in early 1204 to crown him king.

Kaloyan sent envoys to the crusaders who were besieging Constantinople, offering military support to them if "they would crown him king so that he would be lord of his land of Vlachia", according to Robert of Clari's chronicle. However, the crusaders treated him with disdain and did not accept his offer.

The papal legate, Brancaleoni, travelled through Hungary, but he was arrested at Keve on the Hungarian–Bulgarian frontier. Emeric of Hungary urged the cardinal to summon Kaloyan to Hungary and to arbitrate in their conflict. Brancaleoni was only released at the Pope's demand in late September or early October. He consecrated Basil primate of the Church of the Bulgarians and Vlachs on 7 November. Next day, Brancaleone crowned Kaloyan king. In his subsequent letter to the Pope, Kaloyan styled himself as "King of Bulgaria and Vlachia", but referred to his realm as an empire and to Basil as a patriarch.