DuPont Co. said Tuesday that it is indefinitely delaying the commercial launch of the genetically-modified soybean seed at the center of a long-running court battle with archrival Monsanto Co.

DuPont's Pioneer Hi-Bred seed unit had been telling Wall Street that it would launch the Optimum GAT soybean line in 2013 or 2014.

The seed, the launch of which has been delayed before, is controversial because DuPont, a Wilmington, Del., chemicals concern, is using a Monsanto gene in the soybean plant against the wishes of Monsanto, a crop-biotechnology giant based in St. Louis.

DuPont's Pioneer unit said Tuesday that the soybean plant is in limbo because Monsanto refuses to give foreign regulators access to data necessary for the genetically modified crop to win import approvals. The interest of U.S. farmers in growing Optimum GAT soybeans would be severely limited if foreign countries don't accept them: about half of U.S. soybeans are exported.

Scott Partridge, a Monsanto vice president, said Tuesday that Monsanto offered more than a year ago to give DuPont permission to use the Monsanto gene in Optimum GAT soybean seed, as well as access to regulatory data, in exchange for compensation.

"That offer is still on the table, and we remain open to dialogue with DuPont," Mr. Partridge said.

Monsanto filed a patent-infringement suit over Optimum GAT in 2009 against DuPont, which then made anticompetitive allegations against Monsanto in the same St. Louis federal courthouse.

The court fight, which is still under way, attracted the attention of the Obama administration's Justice Department, which in January 2010 opened a formal antitrust investigation into Monsanto's handling of the most widely planted genetically modified crop in the U.S., herbicide-tolerant soybeans.

DuPont's Optimum GAT seeds are genetically modified to grow into soybean plants able to survive exposure to glyphosate-based weedkiller as well as another herbicide called acetolate synthase.

DuPont initially touted Optimum GAT to farmers as an alternative to them buying seeds equipped with Monsanto's gene for surviving glyphosate, the active ingredient in Monsanto's Roundup weedkiller. But Pioneer scientists ended up stacking Monsanto's Roundup Ready gene with their own glyphosate-tolerate gene.

Monsanto argues in its lawsuit that the 2002 licensing agreement giving Pioneer access to Monsanto's Roundup Ready gene prohibits Pioneer from stacking it with any other company's glyphostate-tolerant gene in the same plant.

DuPont interprets the 2002 contract differently and argues that any such gene-stacking prohibition would be illegal.

"Monsanto has never made a good-faith offer to settle this case," said Doyle Karr, a spokesman for DuPont's Pioneer Hi-Bred unit. "Pioneer negotiated for, and received, broad stacking rights in 2002. There is no reason to pay twice for rights Pioneer has already acquired."