The "Annunciation" is one of Leonardo's early works, painted between 1472 and 1475 when the master was in his early 20s. It depicts the archangel Gabriel revealing to the Virgin Mary that she is pregnant.
In protesting the loan, Sen. Paolo Amato said it exposes a priceless masterpiece to unnecessary risk and belittles its significance by using it in a commercial event.
Inside the museum, the 6 1/2-foot-by-3-foot painting was being bundled in three protective crates filled with shock absorbers and high-tech sensors to monitor humidity, temperatures and stress levels in preparation for departure Tuesday.
The 15th century masterpiece will be shown from March 20 through June 17 as part of "Italian Spring," a series of events promoting Italian culture and products.
Art historians and intellectuals from Florence, including the filmmaker Franco Zeffirelli had signed a petition asking Culture Minister Francesco Rutelli to cancel the loan.
Conflicts over managing and showcasing Italy's countless cultural treasures are frequent and loans of masterpieces to foreign countries are a known anxiety factor.