The French Foreign Ministry summoned Ukrainian Ambassador to France Olexander Kupchyshyn and expressed concern over the detention of Ukraine's former prime minister Yulia Tymoshenko and the course of the trial against her, the ministry said on Thursday. The ambassador was told of "the serious concern generated by the detention of Mrs. Yulia Tymoshenko and more generally of the progress of (her) trial." Ukraine has been seeking a revision in the 2009 gas deal with Russia since last spring, saying that the contract's gas price formula is unfair. Russia has tied the price for gas to the international spot price for oil, which has been rising strongly until recently due to the instability in the Middle East. The contract was signed by Tymoshenko who is currently on trial on charges of abuse of office for concluding the deal on terms disadvantageous to Kiev.