EU regulators will decide this week whether to force testing of all U.S. long-grain rice imports to prove the absence of a genetically modified (GMO) strain not allowed in Europe, an official said on Monday.

Earlier this month, the European Commission set a 15-day period for negotiating a common sampling protocol with U.S. authorities to detect the GMO rice strain, which has turned up in the food chains of at least nine EU countries since August.

That deadline expires on Thursday. If no deal is reached, the EU-25 is expected to order compulsory testing of U.S. rice cargoes that arrive at any EU port -- at the exporter's cost.