Ho Chi Minh City authorities have asked the prime minister to increase the investment in the city's first metro rail to over US$2.49 billion.
In its proposal, the HCMC People's Committee asked that official development assistance (ODA) loans be raised to some $2.2 billion accordingly.
The project began last August.
Authorities attributed the projected increase in costs to inflation in material costs, raises in the minimum wage, and changes in the original design.
The 19.7-km route connecting Ben Thanh Market to Long Binh Ward in District 9 was first estimated to cost approximately $1.1 billion, 83 percent of which came from Japan's ODA.
The first of HCMC's six planned metro routes are set for completion in 2013. Operation is supposed to commence in 2014.