Japan will send a large helicopter carrier to the South China Sea and Indian Ocean for a second straight year as it looks to bolster its presence in the strategic maritime region with annual tours, two Japanese officials said.

"This is part of Japan's efforts to promote a free and open Indo-Pacific," said one of the officials, who has direct knowledge of the plan for a two-month tour beginning in September.

The 248 meter-long (814 feet) Kaga, which can operate several helicopters simultaneously, will make stops in Southeast Asian countries such as Indonesia and at ports in India and Sri Lanka, said the sources who asked not to be identified because they are not authorized to speak to the media.