The Tokyo District Public Prosecutor's Office said it will send a special seven-member team to Oman where the men are being held to bring them back to Japan, The Yomiuri Shimbun reported Wednesday.
The oil tanker Guanabara was about 328 nautical miles southeast of the southern coast of Oman Saturday when it was overpowered by pirates.
The destroyer USS Buckley and a Turkish warship responded to a distress beacon sent out by the tanker Mitsui O.S.K.
A special unit from the Buckley overpowered the pirates, Japan's Transport and Tourism Ministry said.
A spokesman for the ministry said the tanker wasn't damaged and none of its 24 crew members was injured.
The government's decision to bring the four suspects to Japan followed a request by the United States, government officials said.