Anthony Joshua could defend his heavyweight world titles against Kubrat Pulev in a Roman amphitheatre in Croatia.
The rivals were due to clash on June 20 at the Tottenham Hotspur Stadium but the coronavirus crisis has put the fight on hold.
The bout is unlikely to take place in the UK as crowds are not expected to be allowed into arenas until the end of the year.
Joshua's promoter Eddie Hearn is considering taking the fight to the Middle East, but Pulev's manager Ivaylo Gotsev has held talks about hosting it closer to home in August or September.
"We have given ourselves four weeks to look for a new territory if the situation and measures in England do not change," he said.
"We are discussing Croatia, there is a unique Roman stadium - Pula Arena, there and we are in active talks," he said.
"We like this option because it is in Europe, in the middle of the continent. The arena itself predisposes to an unprecedented event in our time. There will also be an opportunity for spectators with the right measures taken.
"There needs to be a mutual agreement. We want the terms and conditions to be beneficial for both parties.
"They can't meet in Bulgaria because Joshua will not agree. He wanted to fight at home but force majeure brought a change. Kubrat, however, was ready to fight in Joshua's backyard, even if the judges were his family."
The Pula Arena has a capacity of 5,000 and frequently hosts concerts while Croatia has recorded just over 2,000 coronavirus cases with 85 deaths, compared to over 30,000 in the UK.
