Following the removal of Liu and later the ministry's deputy chief engineer Zhang Shuguang - both leaders in China's high-speed railway development - the ministry faced doubts and pressure from many sides.

Some believed the ministry will not be able to pay back the huge loans it borrowed from banks for building the massive high-speed rail network, while others suspected the stunningly fast construction of the high-speed railways might generate potential safety hazards.

As to the solvency of the ministry's affiliated companies, Sheng said on Saturday that the 1.8-trillion-yuan ($274-billion) debt used for building the country's massive high-speed rail network was still "at a controllable level".

"I believe the high-speed rail market will be rosy" after many projects still under construction are put into service, he said.

As for whether the ministry should build so many high-speed railways in only a few years, Wang Mengshu, a professor at the Research Center of Tunnel and Underground Engineering at Beijing Jiaotong University and a deputy to the NPC, said that forming a network in a relatively short period can generate more profits than laying out the railways one by one.

And the quick speed of construction is not likely to affect quality as the key to safety is the rail track, and China has overcome difficulties to make sure the tracks stay where they are for years so that trains will not derail at high speeds, he said.

Zheng Xinli, former deputy director of the policy research office of the CPC Central Committee and a member of the National Committee of the Chinese People's Political Consultative Conference, said that with the growth of the network and people's income, high-speed railways will gradually attract more passengers and eventually begin to make a profit.

By then, paying back the huge debt will not be a problem, Zheng said.

The country has planned to expand its high-speed rail network to 13,000 km by 2012 and to 16,000 km by 2020.

At the end of 2010, the network was already the world's longest at 8,358 km, of which 5,149 km were put into service in 2010.