Swiss agrochemicals group Syngenta may file counterclaims against some of the more than 750 US grain farmers and exporters who have sued the world's largest agrochemicals group over sales of biotech corn seed that disrupted trading with China last year, regulatory documents show.

According to a filing with the US Securities and Exchange Commission, Syngenta is "assessing the scope for potential counterclaims" in response to lawsuits over Agrisure Viptera corn, also known as MIR 162.

In 2014, global grain handlers Cargill and Archer Daniels Midland Co, along with hundreds of farmers, sued the Swiss group for damages stemming from China's rejections of shipments of US crops that contained Viptera corn.

At the time, the trait was approved for planting in the US but not for import by China, a major corn buyer. Imports have since been approved.

The plaintiffs accuse Syngenta of misleading the farm industry about the timeline for import approval by China and blame it for a decline in US corn prices.

In April 2014, the National Grain and Feed Association estimated that Beijing's rejections cost the US agriculture industry at least $1 billion.

Additional farmers are still seeking to take legal action over alleged losses, as a co-lead counsel for clients suing Syngenta, told the news agency Reuters.