The state budget cannot be spent extravagantly, and sovereign bonds cannot be issued excessively or the government will risk the sustainability of public debt, Dung told a meeting on Monday.
Vietnam is slated to build nearly 2,000 kilometers of highways over the next five years, but not a single kilometer will be done if it keeps waiting for funding from the state budget, Dung said.
The country will need a total of around VND1,000 trillion (US$44.52 billion) for transport projects in the period. The government will be able to raise less than 29 percent of that cost estimate, the Ministry of Transport said in a report in July.
In the 2011-15 period, the ministry said it attracted VND186.66 trillion ($8.31 billion) from non-state sources for transport projects.
The combined investment for all projects of the last five years was more than VND370 trillion ($16.47 billion), local media reported.
There have been attempts to deal with funding shortages.
State-owned Vietnam Expressway Corporation, which invests in highways around the country, has recently announced plans to sell operating rights to five expressways, which cost a total of VND125.57 trillion ($5.59 billion) to build.
The company is having difficulties financing two major expressways which link Da Nang City and Quang Ngai Province in the central region, and Noi Bai Airport and Lao Cai Province in the north, news website Bao Dau Tu reported on Tuesday.