China is set to keep rejecting U.S. corn shipments containing an unapproved genetically modified strain at least until the end of March, shrugging off pressure from Washington to swiftly approve the variety developed by crop chemicals giant Syngenta AG. Under Chinese regulations, the earliest approval of the genetically modified MIR 162 strain could be late March, when the agriculture ministry's biosafety committee holds its annual meeting. If no decision is made, the next review would be in June. But authorities may continue curbing imports until the end of April, when annual stockpiling finishes, traders said. China stockpiles a wide range of agricultural commodities from cotton to grains to help support market prices and ensure returns for farmers. China, the world's third-biggest U.S. corn buyer, had turned back more than 600,000 tonnes by the end of last year, or around a fifth of China's total imports in 2013, after detecting the presence of MIR 162. U.S. officials have been urging China to act promptly to approve the variety, known as Agrisure Viptera and developed by Syngenta, the world's largest crop chemicals firm. Beijing started to crack down on shipments late last year, even though MIR 162 has been mixed in with other varieties since China started to import U.S. corn in 2011. The GM strain is designed to offer enhanced protection against crop-damaging insects and is approved in many countries worldwide. Asked how much more U.S. corn could be rejected, China's quarantine bureau said in a fax that strict checks meant rejections could top the volume already affected. It did not specify a figure. The rejections have helped drive down global corn prices , which lost around 40 percent last year, also under pressure from a big U.S. crop, and left exporters scrambling to re-sell cargoes to other Asian nations. Excuse to Block Imports? China has approved 15 varieties of genetically-modified corn for imports and MIR 162 is awaiting approval. Two U.S. grain groups have asked Syngenta to suspend the commercial use in the United States of Viptera and another GM corn variety, Duracade, until China and other U.S. export markets have granted regulatory approval. Syngenta said altering U.S. marketing plans now would have no effect on grain in the system or Chinese acceptance of corn imports. Niu Dun, China's vice agriculture minister, said last month that the strain had not been approved for imports by the ministry so could not be accepted. The move raised speculation that the ban is being strictly enforced to prevent cheap imports in a well-supplied market, but China's quarantine bureau said it has been consistent in its checks on genetically-modified farm products and applying rules. But the rejections come as corn prices on China's Dalian Futures Exchange have fallen more than 14 percent since the domestic harvest started in September. About 2 million tonnes of U.S. corn, already booked by Chinese buyers, have not been loaded and may be cancelled, said a source at an official think-tank, declining to be named. Scrutiny over the strain has also led to rejections of U.S. distiller grains (DDGs), a corn-based feed grain. Some large feed mills met quarantine bureau officials in Beijing last week to urge them that DDG should be exempted since it is a feed ingredient. Officials responded coolly to their calls, said a source with direct knowledge of the issue. Along with plentiful corn supplies, China is also facing sluggish demand after animal feed demand dropped last year for the first time in decades when meat consumption was hit by bird flu outbreaks and food scandals. Ukraine The U.S. Department of Agriculture (USDA) has cut its forecasts for China's imports to 5 million tonnes from 7 million tonnes in the crop year ending in August 2014. China imports corn almost all from the United States. While China is unlikely to issue corn import quotas to state-owned firms for 2014, private mills with 2.88 million tonnes of quotas could turn to Ukraine, traders said. China imported non-GMO corn from Ukraine for the first time in December, buying 108,866 tonnes. China's state stockpiler, Sinograin, has stepped up purchases from farmers in the northeast and is expected to have built up 30 million tonnes by the end of January, analysts said. Sinograin's purchases could top 40 million tonnes by the end of April, bringing total state stocks to more than 70 million tonnes, larger than the combined output of the European Union. "The lifting of the GMO restriction will depend on domestic corn prices and the supply situation. We will have to wait and see after the government ends its stockpiling at the end of April," said one trading executive at a domestic trading house. (Reuters)