McDonald's Corp. said on Thursday it will expand its U.S. test of a plant-based burger it created with vegan meat maker Beyond Meat Inc. to about 600 locations next month.

The restaurants -- in San Francisco, California and Dallas-Forth Worth, Texas — will sell the  McPlant burger starting Feb. 14 for as long as supplies last in order to "help us understand customer demand," the Chicago-based chain said in a post on its website.

Shares of Beyond, which makes the McPlant patty from peas, rice ,and potatoes, opened about 6% higher.

McDonald's initially tested the burger in eight U.S. locations in November.

In December, two Wall Street analysts forecast a major U.S. expansion of the McPlant.