China has agreed to allow imports of Brazilian corn, providing a key market for surging production that has left a surplus of the grain in the South American farming giant, a Brazilian government official said on Wednesday.

China mostly imports corn from the United States but allowed the first major shipment from Argentina in August. Brazil has been working to address China's phytosanitary concerns and prove that there is no risk of bugs or fungi it its crop.

"The agreement signed today enables Brazilian corn to be imported by China," Gleisi Hoffmann, chief of staff for Brazilian President Dilma Rousseff, said via Twitter.

Although China is the world's No 2 corn producer after the United States and should produce 210 million tons of the grain this season, it is expected to expand its corn imports to feed its growing middle class.

In the 2012/13 season, China imported 3 million tons of corn, an amount that should rise to 7 million in the 2013/14 season, according to the US Agriculture Department.

Brazil's corn production has increased by 60 percent in the past 10 years, culminating in a record 80-million-ton crop in the 2012/13 season that left the country with far more corn than it can use domestically.

The agriculture ministry expects that China, eventually, will take up to 10 million tons of Brazil's corn per year. However Benedito Rosa, the director of the department of commercial affairs, told Reuters in September that Chinese imports in the 2013/14 season would likely be small.