BEIJING - High pressure at great depths remains the greatest challenge faced by Jiaolong, China's manned submersible, as it attempts the world's deepest dive later this year.

Chinese manned deep-sea submersible Jiaolong finishes a 5,143-m test dive on Thursday morning July 28, 2011. [Photo/Xinhua]

"Jiaolong will have a 7,000-meter test dive this year, after several improvements in the submersible,” Jin Jiancai, secretary general of China Ocean Mineral Resources Research and Development Association, told China Daily on Friday.

The date for the record-breaking dive has not yet been announced.

Before the attempt at a 7000-meter dive, the submersible will try a 3000-meter dive in the South China Sea in March or April.

Pressure increases one atmosphere (atm) for each 10 meters underwater. One atm means about 10 metric tons of weight on an area of one square meter, Jin explained.

If the dive is successful, it will mean that Jiaolong is capable of reaching almost all of the world's seabed, and will make China the record holder, surpassing Japan, whose Shinkai 6500 reached a depth of 6,527 meters in August 1989.

Jiaolong carried three people to a depth of 5,188 meters in international waters in the northeastern Pacific last year, indicating that the submersible is capable of reaching more than 70 percent of the Earth's seabed.