Logging operations in the world's largest rainforest dropped by about a third this season, President Luiz Inacio Lula de Silva told a news conference on Thursday.
Satellite estimates indicated 13,100 sq km were cleared in the year to July 2006, compared to 18,790 sq km in the previous season, he said.
Lula was speaking three days before the second run-off round of a general election takes place on Sunday.
The president, who has been criticised by some environmental groups for not doing enough to save the rainforest, usually leaves the announcement of rainforest statistics to Marina Silva, the environment minister.
Lula is expected to defeat opposition candidate Geraldo Alckmin in Sunday's second round of voting.
Last month, Silva gave preliminary estimates of an 11 per cent drop in deforestation, with 16,700 sq km cleared versus 18,790 sq km the previous year.
The new estimate was based on more accurate satellite data. But only two-thirds of the data have been collected and final figures will not be ready before the end of the year.
Land-clearing in the Amazon surged after Lula took office in 2003 largely because a boom in world demand for Brazilian commodities tempted ranchers to graze more cattle, farmers to plant more soy and loggers to fell more trees.
In 2004, an area of rainforest the size of Massachusetts was lost, but land-clearing slowed by a third the following year as the global demand for commodities slowed.
Deforestation is difficult to track because of the Amazon's vast size and because many small wildcat miners and loggers fell trees.