The defense lawyers alleged bias by the magistrates in Milan, Italy's ANSA news agency reported.
Should the claim of "legitimate suspicion" of bias be upheld, the trial will be moved to the closest major city -- Brescia, ANSA said.
Berlusconi is on trial for allegedly having sex with an underage Moroccan prostitute named Ruby. He is also appealing a conviction on tax fraud charges related to film rights involving his Mediaset media group.
Members of Berlusconi's People of Freedom party Monday staged a protest in the Milan courthouse, saying persecution of the former prime minister has been stepped up since the Italian general election in late February.