High underwater pressure will be the greatest danger that Jiaolong, China's manned deep-sea vessel, will contend with when it attempts to make the deepest dive on record this year, a senior official said.

"Jiaolong will make a 7,000-meter test dive this year after several improvements are made to the submersible vessel," Jin Jiancai, secretary-general of the China Ocean Mineral Resources Research and Development Association, said over the weekend.

Jiaolong submersible vessel [file photo]

Before attempting the record-breaking dive, the vessel will make a roughly 3,000-meter test dive in the South China Sea in March or April, he said.

He did not say when the 7,000-meter dive is to take place.

Underwater, pressure increases at the rate of one atmosphere for every 10 meters of depth. One atmosphere is equal to about 10 metric tons of force per square meter.

If the planned dive is successful, Jiaolong will have proven itself capable of reaching nearly any seabed in the world. China will also hold the record for performing the deepest dive, surpassing Japan, whose Shinkai 6500 dove 6,527 meters in August 1989.

Jiaolong - designed to reach a maximum depth of 7,000 meters - carried three people to 5,188 meters below sea level in a test dive in international waters in the northeastern Pacific Ocean last year, indicating the vessel is capable of reaching more than 70 percent of the planet's seabeds.