The submersible has a special titanium hull to withstand the crushing pressures of the deep ocean. If the current expedition is successful, the craft is expected to try operating close to its maximum depth of about 7,000 meters in 2012, making it capable of reaching the bottom of almost all the world's sea areas.

This would elevate China to the top of an exclusive club of deep-sea submersible operators, putting it ahead of Japan, Russia, France and the United States.

China says one of its main aims is to be in prime position to explore and exploit what experts say is a treasure trove of trillions of dollars of gold, copper, lead, zinc, nickel, manganese, cobalt, iron and other minerals in rich reserves on the seabed of the ocean, which covers more than two-thirds of Earth's surface with an average depth of 4,000 metres.

Sustained rapid growth of China's economy requires access to ever more resources. Chinese leaders are looking to the oceans and seabed as a key frontier for the future, in case supplies on land run short or are withheld in a crisis. Some seabed deposits are also richer than those on land, among them deposits of gold, which is currently fetching near record prices, and cobalt, used to make corrosion-resistant light, strong metal alloys and paints.

China hopes to use superior deep ocean technology to increase its influence and leverage over resource control in territorial disputes with several Southeast Asian countries and Japan in the South and East China seas. This aim was symbolized when the Jiaolong used a robotic arm to plant a Chinese flag on floor of the South China Sea during one of its 17 dives in May and June 2010, the longest of which lasted over nine hours.

China also wants to tap reserves of natural gas in frozen hydrate form in offshore areas it claims and in international waters. Chinese scientists say that have found huge hydrate deposits in the South China Sea.

As the Jiaolong and its support ship prepared to leave port on July 1, Jin Jiancai, secretary general of the China Ocean Mineral Resources Research and Development Association, said that part of the mission was to fulfill a contract between the Association and the International Seabed Authority (ISA), an autonomous inter-governmental body linked to the United Nations that regulates mining in international waters.

The ISA is meeting July 11-22 at its headquarters in Kingston, Jamaica. It's consider approving four new applications for deep-sea mineral exploration in the International Seabed Area. They are from China, Russia, Nauru and Tonga. The two Pacific island-states are sponsoring private mining companies, the first time such applications have been made.

The applications from China and Russia are for polymetallic sulphide exploration, also a first for the ISA. Polymetallic sulphides contain mainly copper, lead, zinc, gold and silver. They form massive deposits that can range up to 100 million metric tons. High concentrations of base metals (copper, zinc, lead), and especially precious metals (gold, silver), in some of these deposits have recently attracted interest from the international mining industry as advances in offshore exploration and mining technology brings them within reach.

Most of the 100 sites located so far are in the Pacific but only about 5 percent of the seabed worldwide has been systematically searched.

Jin said that the Jiaolong's mission included taking photographs and video footage of the sea floor, and measuring submarine topography and geology, in a 75,000 square-kilometer area designated by the ISA. "With permits from the ISA, China will be able to explore (for) minerals and other resources for commercial purposes in this area once the technology matures," he added.

The mineral potential of the deep ocean seabed was underscored on July 3 when a group of Japanese specialists announced the results of a seabed survey of 78 sites in the Pacific containing rare earth minerals that are critical to a wide range high-technology products for both civilian and military use.

They estimated that a one square-kilometer area in one hot spot alone held a cache of rare-earth oxides equivalent to one-fifth of current global demand in a market where China produces around 97 percent of the supply and has sent prices sky rocketing by imposing increasingly tight export quotas.

China's ambitious deep ocean exploration and development program only began in 2002. It is a well-funded, high priority venture involving more than 100 research institutes and companies.

As part of the program, China will launch its second marine remote-sensing satellite later this year at about the time it begins construction of a national research base in the coastal city of Qingdao to accelerate the study and search for deep-sea energy and mineral resources. The Jiaolong and its mother ship will be home-ported at the base. China is also expected to build its own deep-sea drill ship and a network of automated observatories on the ocean floor.

While China makes no secret of its deep-sea mineral and energy ambitions, it has said little about the military potential. However, the stated capabilities of the Jiaolong indicate that it could perform key missions for China's armed forces and national security agencies.

They include tapping into foreign undersea fiber-optic communication cables to intercept diplomatic and commercial secrets, recover lost nuclear weapons and missiles, and make high-resolution seabed maps to aid the operation of China's growing fleet of submarines.