"If the yes wins, if the no wins - in any scenario there must be mediation because things aren't working", he told AFP.
"I think that from now it would be logical for the European Union to actively monitor (the situation) and actively take an interest", he said.
But Brussels has preferred to sit on the sidelines of what it views as an internal dispute in Spain.
Teachers, parents, students and activists in the region have leapt into action to defend the vote, defying Madrid's warnings of repercussions by occupying more than 160 schools designated as polling stations.
Catalan Quim Roy, a father of two daughters, is occupying a school with other protesters who have organised picnics, yoga sessions and other activities.
It is still unclear whether the referendum will go ahead despite the regional government's assertions that it will proceed and Madrid's insistence that it will block the move. It has seized ballot papers and drafted thousands of extra police, or Guardia Civil, in a bid to prevent it.
Prime Minister Mariano Rajoy's conservative government has said any vote on Catalan secession would have to be held across all of Spain, not just in Catalonia.
Puigdemont insisted that everything was set-up so that the referendum "takes place normally". In a sign that large crowds are expected on the streets on Sunday, department store chain El Corte Ingles said it would shut three stores in central Barcelona.
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Despite the government shutdown of these polling stations, the Catalan National Assembly has urged voters to still show up if they are blocked by authorities.
"The measures we are witnessing are worrying because they appear to violate fundamental individual rights, cutting off public information and the possibility of debate at a critical moment for Spain's democracy". The regional police had been ordered by central Madrid to help prevent the vote, according to reports. Some shouted "Long live Spain!" and "Puigdemont to jail!"
According to the results of the survey, the vast majority of Catalan citizens, despite the deep divisions over independence, are eager to go to the referendum and finally resolve the issue. "But what Catalan authorities have promised, an effective referendum with legal basis and binding, is something that won't happen".
It will be interesting to see what the future holds for FC Barcelona if Catalonia gets its independence. Farmers and firefighters have vowed to protect polling stations.
The referendum's success or failure could be down to how Catalonia's 17,000 regional officers respond to their orders from the Spanish government.
Catalan officials are expecting a roughly 60% turnout Sunday, meaning in excess of 3 million voters will be at the polls.
Police have been ordered to stop ballots from being cast on Sunday and have been cracking down for days, confiscating ballots and posters.
"[It is] a Spanish problem in which we can do little. It's a problem of respecting Spanish laws that Spaniards have to resolve".
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There is only one way to go for my money though and that is to oppose the visitors at their short price of [1.7]. It will be a tough task for CSKA to deal with United while they're playing in this kind of form.