Peruvian prosecutors are seeking a 30-year jail sentence for self-exiled former president Alberto Fujimori.
Fujimori has both Japanese and Peruvian nationality
They accuse him of ordering 25 people killed by the La Colina paramilitary death squad in 1991 and 1992.
Mr Fujimori, who fled in November 2000 after being toppled in a corruption scandal, denies wrongdoing and says he is a victim of political persecution.
Peru is working to have him sent back, but he is a citizen of Japan, which bars the extradition of its citizens.
He claimed citizenship when he arrived in Japan, based on the fact that his parents were born there.
Mr Fujimori is wanted in Peru on charges including murder, kidnapping and inflicting grievous wounds.
The prosecution's 86-page sentencing recommendation will be added to an extradition request that already runs to more than 700 pages.
In Feburary the Japanese foreign ministry appeared to rule out extradition.
No extradition treaty
"The Japanese government's basic stance is that... we cannot hand someone with Japanese citizenship
over to a country with which we do not have a criminal
extradition treaty under current laws," spokesman Hatsuhisa Takashima said last month.
But Japanese officials later offered a Peruvian delegation more hope, saying Japan had still not made a final decision.
Mr Fujimori is under tight security in Japan
"We don't plan to discuss our conclusion on whether or not the extradition can take place," said a spokesman.
The murder charges against the former president relate to two massacres during his war on the left-wing Shining Path rebel group.
He is alleged to have authorised death squads to carry out the killings of 15 suspected guerrillas in 1991 and nine students and a professor in 1992.
He also faces allegations of corruption stemming from his 1990-2000 rule.
Mr Fujimori rejects all the charges.
He has said he is planning a political comeback in Peru, and hopes to run for the presidency in 2006.