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A controversial new biotech corn developed by Dow AgroSciences, a unit of Dow Chemical,, will be delayed at least another year as the company awaits regulatory approval amid opposition from farmers, consumers and public health officials.

Dow AgroSciences officials said Friday that they now expect the first sales of Enlist for planting in 2014. Previously officials had set the 2013 planting season as a target, but U.S. farmers are already buying seed for planting this spring, and Dow has yet to secure U.S. approval for Enlist.

Dow wants to roll out Enlist corn, and then soybeans and cotton to be used in combination with its new Enlist herbicide that combines the weed-killers 2,4-D and glyphosate. The Enlist crops are genetically altered to tolerate treatments of the Enlist herbicide mixture. The hope is that Enlist will wipe out an explosion of crop-choking weeds that have become resistant to glyphosate alone.

Opponents have bombarded Dow and U.S. regulators with an array of concerns about Enlist, which is intended to replace Monsanto Co.’s successful Roundup Ready system. Genetically altered Roundup Ready corn and soybeans now dominate the U.S. corn and soybean market.

But as Roundup Ready crops have gained popularity, millions of acres of weeds have developed resistance to Roundup herbicide, causing farmers to use higher quantities of Roundup and other herbicides to try to beat back the weeds.

Critics warn that adding more herbicides to already resistant weed populations will only expand and accelerate weed resistance. Some have likened the problem to a “chemical arms race” across farm country.

“Weed resistance to chemical herbicides is one of the biggest problems farmers now face, and that is a direct result of converting so much of our farmland to herbicide-resistant GE (genetically engineered) crops,” said Marcia Ishii-Eiteman, senior scientist at Pesticide Action Network. “We need to get out of this futile chemical arms race fast.”

Earlier this month, Kansas State University scientists said they have found evidence that some more weed types have developed resistance to glyphosate. Researchers said they sprayed two common weed types, Waterhemp and Palmer amaranth, with up to four times the typical field use for glyphosate and the weeds would not die.