"We aren't going to immediately reform the Champions League or the UEFA Cup but must consider it at some time," Aigner said in The Guardian ahead of a two-day meeting of UEFA's executive committee starting on Thursday in Lausanne, Switzerland.
"I'm convinced the Champions League is too long and the fixture list is saturated. We don't want people to get bored and it's important the competitions are interesting," he added.
Despite a rise in attendances for this season's first group stage, there are concerns that bigger clubs such as Lazio, Bayern Munich and Juventus are playing home ties in half-empty stadia.
Another worry is that television audiences were down in all the major markets except Germany.
The current 32-team format was introduced last season under pressure from top clubs, who had threatened to break away from UEFA and form their own league unless they had better access to the highly lucrative European competitions.
UEFA's head of communications Mike Lee said there are unlikely to be any changes made for at least another two years because of the need to honour existing commercial and television deals.
"The season after next is a possibility, but I wouldn't say a strong possibility," he said.
This week's UEFA executive committee meeting will also consider a proposal from the Belgian soccer authorities that a group stage be added to the UEFA Cup.
The revised plans for a 'Euroleague' put forward by major clubs in the Netherlands, Scotland, Belgium, Portugal and Denmark - including former European champions Ajax Amsterdam and Glasgow Celtic - will also be discussed.
Reuters
UEFA chief executive Gerhard Aigner says that the Champions League needs to be reformed to prevent fans losing interest in the tournament, according to a report in a British newspaper.
