Chinese manned submersible Jiaolong is to conduct trial scientific missions between June and September, an official with the State Oceanic Administration (SOA) announced on Thursday.

The four-month work, including research in the South China Sea and the northeast Pacific Ocean marks the start of a five-year trial period for Jiaolong before it starts regular operation, said Jin Jiancai, office director of the China Ocean Mineral Resources Research & Development Association under the SOA.

Jiaolong completed a record dive of 7,062 meters in the Pacific Ocean's Mariana Trench in June 2012, enabling China to conduct deep-sea scientific research and resource exploration in 99.8 percent of the world's oceans.

"During the missions, we will make use of Jiaolong's unique capabilities and technical excellence to obtain high-quality deep-sea information and samples," Jin said.

However, the official revealed Jiaolong is not ready for regular operation as its mother ship has yet to be built and its oceanauts and maintenance team still need training.

Jin added that more efforts will be made to domestically produce spare parts for the sub, and that a national deep-sea base is still in the design stage -- both are factors delaying Jiaolong's regular service.

According to Jin, the difficulty of the trial missions will upped gradually, with safety being the top priority.