In an interview published on Monday, Romani Prodi claimed last week's deadly bomb attack in Madrid showed the negative impact of Iraq's invasion.
"It is clear that using force is not the answer to resolving the conflict with terrorists," Prodi was quoted as saying in the daily La Stampa.
"We must remember that it has been a year since the war in Iraq started. Terrorism is infinitely more powerful than a year ago."
He added all of Europe "felt under attack" after last Thursday's bomb blasts in Spain that killed 200 people and injured almost 1500.
Prodi also raised the possibility of the European Union creating a position for an EU commissioner in charge of ending terrorism.
"We must remember that it has been a year since the war in Iraq started. Terrorism is infinitely more powerful than a year ago"
European Commission president
"This event forces European countries to come up with a joint action plan. In Madrid, there are explicit demands from the population for Europe to ensure people's security and protection."
Need for cooperation
Prodi said the issue was likely to be raised at a scheduled EU summit in Brussels next week.
He said he felt "encouraged" by changes taking place in the US which appeared more willing to cooperate with the rest of the world.
"All the Democrats and some Republicans believe that the United States must cooperate with other countries and should act alone only in exceptional circumstances."
"It is not Europe which is getting closer to the United States but rather America which is moving toward us."