Ukraine has warned it could seek international arbitration over restrictions on its grain exports after Poland said it would continue to block domestic imports of Ukrainian grain even if Brussels lifts a ban.

Restrictions imposed by the European Union in May allowed Poland, Bulgaria, Hungary, Romania and Slovakia to ban domestic sales of Ukrainian wheat, maize, rapeseed and sunflower seeds, while permitting transit of such cargoes for export elsewhere.

The restrictions, designed to ease excess supply, are due to expire on Friday.

Poland, which holds a parliamentary election on October 15th and says cheaper Ukrainian grain makes domestic production unprofitable, has said it will not lift its ban even if the EU does not extend the arrangement this week.

The five central European countries want the EU ban extended at least until the end of the year.