KIEV, October 11 - RAPSI. A representative of the United Energy Systems of Ukraine (UESU) has doubts over the existence of letters from 1996 by the then Prime Minister Pavlo Lazarenko which gave government guarantees for UESU liabilities to the Russian Defense Ministry.

On Thursday, the Kiev Economic Court of Appeals will continue to hear the complaints filed by the Ukrainian Finance Ministry, State Treasury and UESU against the trial court order to the government to pay UESU's debt. The copies of Lazarenko's letters to the Russian government served as one of the grounds for the ruling.

"There are doubts as whether these letters ever existed in the first place," said UESU representative Alexander Kovalchuk at the court session. He stressed that he had requested to see the original letters previously.

He added that as the original letters were not examined at the trial court, this puts the validity of its judgment in question.

On September 19, the Kiev Economic Court partially ruled for the Defense Ministry's suit, obligating the Ukrainian government to pay more than 3.2 million hryvnas ($390 million) in UESU debt which arose in the 1990s, when the corporation was headed by Yulia Tymoshenko.

Russia maintains that the debt stems from the UESU's failure to fulfill their 1997 agreement to supply goods for the Defense Ministry.

In October 2011, Tymoshenko was sentenced to seven years in prison for abuse of power based on a 2009 gas contract that she signed with Russia. She is serving her sentence in a Kharkov women's prison. She has been receiving treatment at a Kharkov hospital since May 2012. She was diagnosed with a spinal disc herniation.

In late March, a second case bringing further charges against Tymoshenko was filed with Kharkov's Kievsky District Court. The case deals with her activity at UESU. She is accused of misappropriating funds.