Burger King is selling its soy-based Impossible Whoppers nationwide for a limited time only starting next week.

The fast-food chain first tested the plant-based patties in 59 St. Louis restaurants in April.

The meatless burgers are produced by California tech startup Impossible Foods, which uses an iron-rich molecule called heme to produce veggie patties that "bleed."

Burger King on Thursday said that it will roll out its soy-based Impossible Whoppers nationwide for a limited time starting next week, so that customers can "decide for themselves if it delivers the same flame-grilled, juicy craveability" of its traditional beef Whoppers.

The Miami, Florida-based fast-food company said customers starting Aug. 8 can purchase the plant-based burgers in one of its 7,000 U.S. locations. Diners can also have the Impossible Whoppers delivered via the Doordash or Burger King mobile apps.

A single sandwich on menus retails for $5.59, though customers in-apps can also order a "taste-test," which includes both a traditional beef Whopper and an Impossible Whopper, for a $7 retail price. The promotion in stores will last until Sept. 5 or until supplies run out.

a big deal just became a bigger deal. the Impossible Whopper is available nationwide starting 8/8. pic.twitter.com/TpFQenSLFQ — Burger King (@BurgerKing) August 1, 2019

Burger King first tested the plant-based patties, developed by California tech start-up Impossible Foods, in 59 St. Louis restaurants back in April. It has since tested the burgers in six additional markets and has said it planned to launch the burgers nationwide.

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Impossible Foods, founded in 2011 by Stanford biochemistry professor Patrick Brown, is part of a recent crop of plant-based companies like Beyond Meat targeting meat lovers for its product. The food company uses soy leghemoglobin, an iron-rich molecule typically found in animal protein and called "heme" for short, to mimic the flavor of meat and make meatless patties that "bleed."

The ingredient, which food activists criticize for being genetically engineered from yeast, separately on Wednesday was approved by the U.S. Food and Drug Administration, clearing the way for Impossible Foods to start selling its patties in grocery stores, which the food company said it will do starting September.