Wheat prices have resumed their rally as the prospect of another country limiting exports feeds into supply concerns.

Wheat prices hit a two-year high earlier this month because a severe drought in Russia has destroyed about one-fifth of the grain exporter's harvest. Russia earlier this month suspended exports for the rest of the year because of damage from the weather.

Dryness in Ukraine and heavy rains in Canada have also hurt crops. Ukrainian officials on Wednesday delayed a decision on whether to limit grain exports from September through December because of dry weather hurting the harvest. The announcement is expected on Aug. 25, Barclays commodities analysts said.