Global rice trade in 2012 would fall 7 percent from last year to 32.8 million tons "due to lower import demand by leading importing countries such as Indonesia and Bangladesh", the ministry said in a report.
The lower projection is in line with market expectations, after Vietnam's rice exports in the first two months of this year fell 43 percent from the same period in 2011 to 627,000 tons, based on the Vietnam Food Association data.
Vietnam, the world's second-largest exporter after Thailand, shipped a record 7.1 million tons of rice last year.
The agriculture ministry's forecast is also lower than its last month's projection, which said Vietnam could ship between 6.58 million tons and 7.34 million tons of the grain for the whole of 2012.
Rice exports from Vietnam could fall 44.4 percent in the three months ending March from a year earlier to 1 million tons, a government report said on Monday.
Slowing exports, at a time when the harvest of a major rice crop in Vietnam's Mekong Delta food basket is due to peak in two weeks, could lead to a huge build-up in supply and trigger a fall in domestic prices.