Jakarta. Transportation Minister Budi Karya Sumadi revealed in a press release on Sunday the government's idea to expand the Jakarta-Bandung bullet train service to Surabaya in East Java.

"If the Jakarta-Bandung service proves to be a success, we would consider extending the track to Surabaya," Budi said.

The minister said the government is optimistic construction on the Jakarta-Bandung bullet train network could be completed by the end of 2021. "We aim for full operations by the end of next year," he said.

Progress on the construction of the bullet train track has now reached 44 percent. Land acquisition is 99.96 percent complete.

Budi has a few words to say for Kereta Cepat Indonesia China (KCIC), the project's contractor. "First, the project must be finished on time. Second, there must be a transfer of technology [from the contractor to local workers]. And third, they have to maintain a good relationship with the public," he said.

KCIC managing director Chandra Dwiputra said unstable soil at several spots on the track in West Java has been the biggest obstacle during the construction.

"Extreme weather conditions are also a big challenge. But we've anticipated them so they will not slow down construction," Chandra said.