A private advisory panel to Prime Minister Junichiro Koizumi kicked off discussions Tuesday on the Imperial House Law, with the central theme to be whether and how a female could ascend to the Chrysanthemum Throne.

Allowing for a reigning empress who marries outside the Imperial family and whose children ascend to the throne would terminate a hereditary tradition in which only those from the paternal line have reigned. The tradition is believed to have continued for more than 1,000 years.

The issue has become a keen topic of interest because no males have been born to the Imperial family for almost 40 years and Crown Prince Naruhito's only child is Princess Aiko, 3.