Mexico has canceled existing sugar export permits that allow supply to get to the United States.

Mexico's sugar industry leaders said the U.S. Department of Commerce is to blame and that unfilled staff positions in the U.S. administration are causing delays in shipments.

Mexico is the U.S.'s top foreign supplier of sugar.

The dispute centers on an interpretation of how the Mexican government issues export licenses to ensure supplies enter the United States at a regulated pace.

According to Reuters, it’s not immediately clear how many sugar export permits were canceled or what penalties Mexico faces.

The letter, sent by Mexico's sugar industry leaders to mills, said existing permits would be reissued in April.