A U.S. farmer group on Tuesday dropped its opposition to efforts by Dow AgroSciences to roll out a new biotech crop system in exchange for some concessions by Dow, including help investigating any accidental crop damage.

The deal calls for "several new safeguards" from Dow AgroSciences related to use of a reformulated herbicide and biotech crops engineered for use with it. While other groups still oppose Dow's crop system, the agreement with the farmer group could speed regulatory approval sought by the unit of Dow Chemical.

The farmer group, called Save Our Crops, represents more than 2,000 U.S. farmers. It had filed legal petitions with the U.S. Department of Agriculture and the Environmental Protection Agency opposing Dow's new crops and herbicide, together dubbed "Enlist."

The group is one of many organizations that have protested the proposed new crop system, citing feared damage and contamination of other crops and harm to the environment and human health.

Strong opposition remains. But Dow officials hope to gain regulatory approval quickly so they can start selling new biotech corn seeds in the next few months, spokesman Garry Hamlin said Tuesday. U.S. farmers generally start buying seed in the fall for planting in the spring, and the selling season is kicking off this month.

"We've been signaling all along that we thought differences like these could be resolved," said Hamlin. "We think we've reached a favorable resolution. We want to be able to provide this to growers for 2013. We recognize that it is September ... but that continues to be our goal."

U.S. agricultural and environmental groups have been in an uproar over Dow's intentions to commercialize new genetically altered corn, soybeans, and cotton that will withstand dousings of the new Enlist herbicide.

The herbicide combines glyphosate with a reformulated herbicide known as 2,4-D that - while long proven as an effective weed killer -- is controversial for its volatile nature and toxic effects, and tangential ties as one of the elements in the "Agent Orange" defoliant used in Vietnam.

Many farmers have protested Dow's move because they fear rising use of 2,4-D will increase the damage already done when 2,4-D drifts on the wind into fields and gardens where it kills not just weeds, but other plants and crops. Dow said it has reduced the volatility and risk of drift with the new formulation.

As well, Dow has agreed to amend its labeling instructions for farmers to specify for applications near sensitive crops. And Dow AgroSciences has committed to assist in investigating any damage claims on non-targeted crops, and in educating growers and applicators in proper application to reduce off target movement, especially in areas with sensitive crops.

Dow also said it commits to pricing both the seed and herbicide technology competitively to reduce the likelihood that farmers will use generic 2,4-D, which does not have the reduced drift and volatility when they spray their crops.

"With this agreement ... we are no longer opposing the Enlist program," said Steve Smith, director of agriculture at Indiana-based Red Gold, the world's largest processor of canned tomatoes, and a leader of Save Our Crops, the coalition that had been battling Dow.

"We think Dow has done a good job understanding the necessity to put several new safeguards in place," Smith said.

Enlist is the first in a planned series of new herbicide-tolerant crops aimed at addressing a surge in weeds that have developed resistance to Monsanto's popular Roundup herbicide.

Roundup use increased dramatically after Monsanto introduced Roundup-tolerant, or "Roundup Ready," crops in the mid 1990s. While Roundup once killed weeds easily, experts say that even heavy use of Roundup now often fails to kill "super weeds."

Chemical giant BASF and Monsanto plan to unveil by the middle of this decade crops tolerant to a mix of the chemicals dicamba and glyphosate. Smith said his group remains opposed to the dicamba product.

Many critics remain opposed to 2,4-D-tolerant crops. Among other things, they are concerned that greater use of 2,4-D, will add to increased weed resistance. And several medical and public health professionals have expressed concerns that increased use of 2,4-D could be harmful to humans.

Critics have cited studies that report an association between exposure to 2,4-D and non-Hodgkin's lymphoma, a cancer of the white blood cells that can be fatal. 2,4-D has also been linked to birth defects, neurological damage in offspring, and interference with reproductive function, according to critics.

There is also great concern that the new biotech crops will contaminate conventional and organic crops.

The USDA has received more than 450,000 comments opposing approval of the 2,4-D tolerant cropping system, according to the Center for Food Safety, which opposes approval.

"Opposition remains. This deal is a real disservice to those of us who are trying to get responsible regulation on this," said Andrew Kimbrell, executive director of the Center for Food Safety, which has threatened to sue the government if it approves the new Enlist crops. "We will sue."