China will begin its selection process this year for the next generation of astronauts who will train to work on the country's planned space station, a senior official said.

Yang Liwei, deputy director of the China Manned Space Agency and the first Chinese astronaut in space, said the selection work will begin soon and that Chinese scientists and engineers will be eligible to apply.

"We plan to select suitable candidates from space industry companies, research entities and universities and train them into engineers and payload specialists capable of working on the space station," he said during an open day at Beijing's Astronaut Center of China. 

"Those who want to apply for an engineer's post will need a master's degree, while candidates for payload specialists will need a doctoral degree," he said. "They will also have at least three years of work experience."

Yang did not discuss other criteria for the new generation of astronauts, such as their physical and psychological conditions.

China is developing and building parts of a manned space station and plans to start assembling it in space starting in 2020. The station is scheduled to become fully operational around 2022, according to Yang's agency.

As the nation's largest asset in the universe, the station will have three parts — the core module attached to two space labs, each weighing about 20 metric tons — and will be in service for at least 10 years, the agency has said.

China began to select its first generation of astronauts in 1995 and picked 14 from more than 1,500 experienced PLA Air Force aviators. In 2009, selection for the second-generation of astronauts, also from Air Force pilots, was launched. Seven passed all tests and were recruited. 

In selecting the first two groups, candidates had to be age 25 to 35, have a height ranging from 160 to 172 centimeters, a weight between 55 and 70 kilograms, and have at least 600 hours of aircraft flight. 

Five astronauts in the first generation retired in March 2014 because they were no longer suitable for spaceflight, so there now are 16 astronauts in active service. 

In addition to its own spacemen and women, China also is willing to help other nations select and train astronauts and will gladly cooperate with them in its space station program, Yang said. 

In an earlier interview, he said more than 10 countries, mostly among developing nations, have asked for China's assistance in selecting and training astronauts. They hope to prepare astronauts for prospective joint missions to China's planned space station, he said.

Yang said China welcomes other parties to join the space station program for mutual benefit and the peaceful use of outer space.