...Executive Martin Roman told Reuters on Thursday.
CEZ and MOL announced last week they would form an alliance to build power plants in central and southeastern Europe.
"It is a complicated structure. The exact size of the stake will be published when the contract is signed, which should be within a few months," Roman said on the sidelines of a business conference in the southern Polish town of Krynica.
CEZ said in a statement when the deal was first announced that it was considering taking an up to 10 percent stake. The shares would come from MOL itself.