CHINA is continuing to reject unapproved genetically-modified US corn exports, and is expected to either buy in future larger quantities from Ukraine where the grain is cheaper, or dip into the huge state reserves.

The rejection of US corn is fuelling speculation that China's ban is being strictly enforced to prevent cheap imports in a well-supplied market, reported Reuters.

China's quality watchdog in the northern city of Tianjin refused 21,800 tonnes of US corn after detecting MIR 162, a GMO strain developed by Syngenta AG that Beijing has not approved for import.

That brings the total amount of corn that China has rejected from the United States, the world's largest exporter, to 908,800 tonnes since November.

"The industry is not optimistic over imports from the United States. Resolution of the GMO issue could drag on until the second half of the year," an industry analyst with an official think-tank in Beijing was quoted as saying.

In response to claims that China is blocking cheap imports, the nation's Quarantine Bureau has said it has been consistent in its checks on genetically modified farm products and applying rules.

China holds 90 million tonnes of corn in state stockpiles, with the market expecting it to sell grain in May.

Firms that have quotas for low-tariff imports are shifting to Ukraine and Thailand for supplies, analysts said.

China's imports of non-GMO corn from Ukraine rose to 192,374 tonnes in February, bringing the country's total imports in the month to 479,758 tonnes, an increase of 22 per cent on the year, according to official customs data.

The China National Grain and Oils Information Centre (CNGOIC) estimated total imports from Ukraine this year could reach 800,000 tonnes.

China also imported 77,936 tonnes of corn from Thailand in February.