BEIJING -- China began test Thursday to restore the maximum speed of bullet train on the Beijing-Shanghai high-speed railway to 350 kilometers per hour, six years after it was was reduced to 300 kmh.

Departing Beijing South Railway Station at 8:38 am, a Fuxing bullet train will complete the round-trip from Beijing to Xuzhou, some 700 kilometers away, within about four hours.

The speed hike will cut the Beijing-Shanghai journey to about 4.5 hours, about half an hour faster than the current minimum between the two cities.

If successful, the test will pave way for a new schedule on the Beijing-Shanghai railway starting in mid-September.

Connecting the Chinese capital with its major financial and trade hub, the Beijing-Shanghai high-speed railway is one of the busiest in the country, carrying over 100 million passengers a year.

China has the world's longest high-speed rail network, 22,000 kilometers at the end of last year, about 60 percent of the world's total. Chinese bullet trains have been bought by countries including Indonesia, Russia and India.