"They're going to have to rearrange some of the sweetheart for one side and poison pill for the other" deals signed by President Leonid Kuchma and Russia, said the official speaking on condition of anonymity.
He cited the example of a gas consortium agreement signed last year, details of which are still unknown to senior members of the Ukrainian government.
"My guess is ... the reason why this thing is so non-transparent is because it's an abomination to Ukraine's interests," he said.
The official also said the Odessa-Brody pipeline, which pumps Russian crude to the Black Sea port of Odessa, went against Kiev's interests because, among other things, it lacked standard oil pipeline clauses.
Russia is Ukraine's largest trade partner and energy supplier.
He added, however, Ukraine wanted to have relations with Moscow based on "reciprocity and mutual interest," but noted: "They don't want to confront the West with a basketful of Ukrainian-Russian problems."