Farmers from the biggest U.S. corn-growing states have sued Syngenta AG over sales of genetically modified corn seed not approved by China, joining global exporters in pursuing damages from the Swiss-based company.

In coordinated lawsuits filed on Friday in federal courts in Iowa, Illinois, Nebraska, Kansas and Missouri, farmers accused Syngenta of being reckless when it launched U.S. sales of Agrisure Viptera corn seed in 2011 without obtaining import approval from China, a major buyer.

The farmers, who did not plant seed containing the unapproved trait, claimed they suffered losses because the price of U.S. corn dropped when China began rejecting boatloads of crops containing Viptera corn last year.

In April, the National Grain & Feed Association estimated that U.S. farmers had lost more than $1 billion due to trade disruptions linked to the rejections.

The lawsuits seek to open the complaints to all U.S. farmers who grew non-Viptera corn since China began rejecting the trait in November 2013.

Viptera corn, known as MIR 162, was planted on about 3 percent of U.S. corn acres during the past two years, according to court documents. Still, industry members have said the trait can be found throughout the supply chain because it is difficult to segregate one variety from another.

"There are a lot of angry farmers out there who really feel like Syngenta needs to step up and do the right thing, and that is compensate farmers for all the losses that occurred as a result of Syngenta prematurely rushing the product to market," said James Pizzirusso, a partner with law firm Hausfeld LLP, which is coordinating the farmers' lawsuits.

Last month, agribusiness company Cargill Inc [CARG.UL] and another exporter separately sued Syngenta for selling Viptera corn seed before Beijing approved imports. The companies said they suffered combined damages of more than $131 million linked to China's rejections of U.S. crops containing the trait.

Syngenta had no immediate comment on the farmers' lawsuits. The company has said the exporters' complaints are without merit.

The U.S. Department of Agriculture is negotiating with China to synchronize its regulatory review of new traits with the United States in a bid to reduce approval times, Agriculture Secretary Tom Vilsack told reporters on Monday after a speech in Chicago.

According to the lawsuit, farmers felt misled about the prospects for China to approve imports of Viptera corn because Syngenta Chief Executive Michael Mack said in an April 2012 earnings call that he expected Beijing to clear the trait "within a matter of a couple of days."

Beijing still has not approved Viptera corn.

"We don't mess with China," Deb Volnek, a Nebraska farmer who is among those suing Syngenta, told Reuters. "When China buys something, the markets go up. When they don't, the markets go down."

Her case is Volnek Farms Inc v. Syngenta Corporation et al, U.S. District Court, District of Nebraska, No. 14-cv-00305.