Paris: French billionaire Francois Pinault and son Francois-Henri Pinault have officially signed documents setting aside €100 million ($163 million) toward rebuilding Notre Dame Cathedral, following months of delay that left officials largely reliant on small charity donations to fund the first phase of repairs.

Surrounded by portraits of former cardinals, the Pinaults signed the donation agreement at the Archdiocese of Paris on Tuesday. The money will give the Notre Dame Foundation a much-awaited financial boost as authorities draw up plans for the cathedral's reconstruction, following the devastating fire on April 15.

Francois-Henri Pinault, CEO of Kering, left, his father Francois Pinault, right, and Archbishop of Paris Michel Aupetit, centre. Credit:AP

Paris Archbishop Michel Aupetit says "everyone gives what he can according to his needs, but the big donors give us breathing room."

Francois Pinault, whose international luxury group Kering owns Gucci and Saint Laurent, pledged the money directly after the fire. His rival, French billionaire Bernard Arnault of luxury goods group LVMH, soon followed suit, pledging €200 million. The Bettencourt Schueller Foundation of the L'Oreal fortune also promised €200 million.