Blanc had previously said he would announce only a final 23-man squad, but has now changed his mind.
The French Football Federation said on its website on Wednesday that Blanc will name the first part of his provisional squad - comprising of foreign-based players - on May 9, before selecting those from the French league on May 15.
Blanc will then trim down his squad by releasing several players.
Teams must name their official Euro 2012 squads by May 29.
This gives Blanc the chance to have one final look at fringe players when France play Iceland in a friendly on May 27. France then has friendlies at home to Serbia on May 31 and to Estonia on June 5.
France, European Champions in 1984 and 2000, face England, Sweden and hosts Ukraine in their group.
France coach Blanc to name larger provisional squad before Euro
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