The French, however, raise safety and environmental concerns as a reason for not allowing heavy goods traffic back into the tunnel straight away.
Rage in Rome
Local people are strongly opposed to the return of lorries to the tunnel, arguing that the air has become cleaner during their absence, and that the snow near the tunnel entrance is no longer stained black.
Mr Bolkestein stressed that the request for France to justify itself did not automatically mean the country was violating its treaty obligations to ensure the free flow of goods, as Italy maintains.
However, the country must provide a satisfactory explanation to its actions before the start of next week.
"We are hoping the French Government will give us a response, and hoping that the obstacles will be quickly removed," Mr Bolkestein said in Brussels after meeting with Italian Transport Minister Pietro Lunardi.
Last week, France put forward its proposal for a "progressive and rapid" reopening of the link to smaller lorries, but that did not impress ministers in Rome.
"There is no physical or technical reason to prevent a total and immediate reopening," Mr Lunardi told the French daily Le Figaro in an edition published on Monday.
"One country cannot penalise another," he said. "The European Union must give us justice."
He also warned of a protest on 7 April by Italian and French lorry drivers if there was no progress.