In a sign the country's ambitions to go faster, higher and bigger have not been dimmed by the end of the Olympics, the Ministry of Railways says it is raising the speed it intends the new line connecting the cities to reach when it opens in 2012.

New technology will enable trains to travel at 380 km or 236 miles an hour, 30 km per hour (18mph) more than the current generation of bullet trains, according to the ministry's deputy chief engineer, Zhang Shuguang.

"It is possible that we can start to manufacture 380 km/h trains in two years' time, and put them into service on the Beijing-Shanghai high-speed railway," he said, according to state media.

The high-speed line from Beijing to Shanghai has been an on-off project for several years, but work finally began in April.

Officials have been torn between improving the extensive and reliable but slow services linking cities across the country and building high-tech lines between major cities. But they have also been encouraged by the initial success of the bullet train that since July has reduced journey times from Beijing to the nearest port at Tianjin to just half an hour.

With China's two most important cities separated by 1,318 kilometres or 819 miles, the new line will be the longest high-speed railway to be built in one go in the world.

The Tianjin route uses 350 km/h trains relying on technology imported from the German engineering giant Siemens. A local company is building up production to 50 trains a year by next year to service both the Tianjin and Shanghai lines.

But Mr Zhang said China's own engineers had "mastered" the technology sufficiently to upgrade the trains' speed further.

The extra would be sufficient to cut the journey time from five hours as currently planned to four hours, compared with current 10-12 hours. The difference would make the rail route competitive with the current two-hour flight time once check-in times were taken into account.