Industry experts attributed declining demand in Vietnam to the fact that firms had stockpiled huge amounts of cement in anticipation of price increases.
Domestic cement consumption in the first half of the year dropped by up to 40 per cent.
The Vietnam Cement Association also said the country was facing stiffer competition from imports.
In response to declining demand, local enterprises have reduced prices by about VND20,000 (U$1.08) per tonne against the previous month.
The current price stands at about VND900,000 to VND1.26m ($48.6-68) per tonne against market estimates of VND950,000-1.15m ($51-62).
The association said that cement productivity last month was 4.4Mt, a decrease of 0.03Mt against the previous month.
Consumption last month reached just 4.3Mt.
Domestic firms said they were having to compete with colleagues from Thailand and China who are charging about 10 per cent less than local producers.
The Building Materials Department said production this year would be about 53Mt, while demand is estimated to be about 50Mt.
Despite the downturn in the market, firms such as Ha Tien and Cam Pha have managed to penetrate markets in Laos, Cambodia and China.
To bolster prices, the industry has asked the Ministry of Construction to stop licensing new cement projects.