* China rejects 9 U.S. corn cargoes in one month
* China urges U.S. to boost checks to avoid contamination
* U.S. officials raised the issue at trade talks this week
By Niu Shuping and Sui-Lee Wee
BEIJING, Dec 20 (Reuters) - China has rejected a total of 545,000 tonnes of corn from the United States as of Dec. 19, after detecting an unapproved genetically modified strain, the government's quarantine authority said on Friday.
The rejection of U.S. supplies by the world's No.3 corn importer could drag on Chicago Board of Trade corn prices which dropped to a three-year low earlier this month.
The volume rejected amount to nine cargoes, accounting for nearly 30 percent of China's expected imports of the grain in November and December, analysts said.
The rejections were due to the presence of the genetically modified strain MIR 162, which is not approved by China's agriculture ministry, the General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) said.
U.S. officials had earlier said they would urge China to act promptly to approve the variety, known as Agrisure Viptera and developed by Syngenta AG.
Officials from the United States have raised the issue with their Chinese counterparts, U.S. Trade Representative Michael Froman told reporters at the end of annual trade talks between the two countries in Beijing.
"He did have discussions with his counterparts around this issue, and more generally, around the issue of developing a regulatory, transparent and reliable regulatory program for dealing with biotechnology events," Froman said, referring to U.S. Agriculture Secretary Tom Vilsack.
"This is an issue that is certainly very much on ... our agenda," said Froman, without giving any further details.
China has already approved 15 varieties of genetically-modified corn for imports and MIR 162 is awaiting approval.
"The safety evaluation process (for MIR 162) has not been completed and no imports are allowed at the moment before the safety certificate is issued," said China's vice agricultural minister, Niu Dun.
China's quarantine authority rejected the first cargo in November after detecting the MIR 162.
The authority has asked the United States to boost checks during production, transportation and at storage facilities to avoid contamination, it said in a statement on its website. (www.aqsiq.gov.cn)
Industry sources said China's strict checks on U.S. cargoes were aimed to curb cheap imports and support domestic corn prices that were pressured by a record harvest and weak consumption.
China faces a glut due to weak consumption by the animal feed industry. Its corn output in 2013/14 is likely to rise 5.9 percent on the year to a record 217.7 million tonnes, surpassing consumption, seen at 197 million.