China's corn imports from the United States, the world's top exporter, decreased sharply in February, hurt by Beijing's rejection of an unapproved genetically-modified (GMO) strain, but imports from Ukraine surged, official customs data showed on Friday.

China imported 205,776 tonnes of corn from the United States in the month, down more than a third from January's imports of 641,843 tonnes, data from the General Administration of Customs showed.

Beijing has since November rejected a total of about 900,000 tonnes of corn from the United States after detecting Syngenta corn strain MIR 162, which is not approved by China's agriculture ministry for import.

But China's imports of non-GMO corn from Ukraine surged to 192,374 tonnes in February, bringing the country's total imports in the month to 479,758 tonnes, up 21.74 percent on year, data showed.

China started importing corn from Ukraine late last year and feed mills continue to book cargoes under a loan-for-grains deal signed in 2012.

China's corn imports in 2013/14 were estimated to rise only slightly to 2.8 million tonnes from 2.7 million tonnes in the previous year, Zhu Yongsheng, assistant general manager of the bio-chemical and bio-energy division of COFCO Ltd told a conference.

"The rejection may cause cancellation of future shipments from United States," said Zhu.

But lower overseas prices have resulted in an increase in imports although China has a glut. China bought its first U.S. corn in more than two months last week after seven consecutive weeks of cancellations, the U.S. Agriculture Department said.

Traders expect Beijing to release its huge reserves of corn as early as May after it has added 60 million tonnes by the end of April to state stocks.