MILAN (Reuters) - The leader of Italy's main opposition party said he was keeping the option of a referendum on the euro open in the event his party won elections and failed to convince Brussels of the need to change some of the euro zone's economic rules.

In comments made on state TV on Sunday, Luigi Di Maio, the man widely tipped to be the candidate for prime minister of the anti-establishment 5-Star Movement, said he wanted to negotiate concessions on EU governance.