U.S. Ambassador Thomas Foley made an official request Thursday to Justice Minister Takao Jinnouchi that work be done toward establishing a bilateral treaty to repatriate prisoners, ahead of a U.S.-Japan leaders' summit in May.

During a courtesy visit to the justice minister, Foley offered concrete suggestions on the issue, proposing that a bilateral agreement be signed or that Japan become a member of the Council of Europe's treaty on returning convicts to their native countries, officials quoted him as saying.

The treaty has 41 signatories, including the United States, the officials said. Such agreements are aimed at relieving the heavy burden of cultural and language differences on prisoners outside their native countries.

Ministry officials have taken up the issue following an earlier U.S. request to that end. The Justice Ministry will continue work on the issue in cooperation with the Foreign Ministry, they added.

The two countries have already signed a treaty to extradite criminals, and the ministry officials said they are also working toward entering a mutual legal assistance treaty.

At the end of 1998, there were 45 Americans imprisoned in Japan, while the number of Japanese serving time in the U.S. was 23 as of January the same year, sources said.