Japan may increase the size of its submarine fleet to meet greater security demands in the Pacific, officials said, amid concerns that the Chinese navy is growing stronger and more likely to tip the regional balance of power.

The Defense Ministry said a bigger submarine fleet is under consideration, with a firm proposal likely to come as early as December.

Officials on Tuesday refused to give further details because the plan has not yet been formally tabled.

According to Japanese media reports, the number of submarines would be increased from 16 to 22 over the next four years, a substantial rise that could generate concern from neighboring China.

Though well outnumbered by the Chinese — who have about 60 subs — the Japanese navy's submarine fleet is significantly augmented by U.S. subs deployed throughout the region. Japanese subs are generally believed to be better equipped than many of the Chinese vessels and are hard to detect.

But concern over China's growing military capablities have been heightened by recent maritime disputes, including a serious row between Tokyo and Beijing over several remote islands in the East China Sea that both countries claim as sovereign terrritory.

A recent Pentagon report said China was likely to sharply increase its own submarine fleet was over the next several years.

It said China is also developing a ballistic missile capable of attacking aircraft carriers more than 930 miles (1,500 kilometers) away and could start construction of an aircraft carrier of its own by the end of the year.