Prodi was speaking ahead of a progress report which the European Commission is due to publish on Wednesday for accession candidates Croatia, Turkey and Macedonia, and potential candidates Bosnia and Herzegovina, Serbia, Montenegro, Kosovo, and Albania. The Commission will also publish a report on a further enlargement strategy.
Prodi warned that any attempt to halt the process for countries such as Croatia and Macedonia threatened to halt the entire exercise, the newspaper read.
"It is impossible to imagine a negotiation with Turkey going on if we stop negotiations with Croatia and Macedonia," he was quoted as saying.
Prodi said he told UK Prime Minister Tony Blair on Monday that "if we want to have a dialogue with Turkey, we cannot miss our mission with the Balkan countries that are ready".
"There is an idea in some parts of Europe to stop it all," the newspaper quoted him as saying. "But I think this is a great historical challenge."