Despite mounting pressure from the U.S. and the European Union, Ukrainian President Viktor Yanukovych has insisted on keeping former Ukrainian Prime Minister Yulia Tymoshenko imprisoned on a conviction of power abuse -- but on Tuesday he promised she will receive medical treatment outside of her Kiev jail within the next two days.

Yanukovych's comments follow  concerns by Ukrainian human rights groups who say the former prime minister has been in poor health, adding that Tymoshenko had been unable to get out of bed over the weekend, but was still being interrogated in her cell, Agence France Presse reported.

Speaking at a news conference with his Lithuanian counterpart, Dalia Grybauskaite, Yanulovych said he was informed by the Ukrainian health minister, interior minister and prosecutors that the health care system in prison has not yet reached a sufficient standard, and the care must be given in medical establishments in Kiev outside prison.

Human rights ombudsman Nina Karpacheva said she visited Tymoshenko in her prison cell on Sunday night and said she was surprised to discover her in bad health, unable to move from her bed to talk with her. According to Tymoshenko's lawyer, Serhiy Vlasenko, the former prime minister has been suffering from severe back pain.

Her condition is extremely serious. She could not get out of bed when talking to me, Karpacheva said in comments released by her office. She needs to be examined and treated outside of prison.

Last month, Tymoshenko, 50, was convicted of abusing her powers while negotiating a natural gas import contract in Russia in 2009 and sentenced to seven years in jail.

The U.S. and the EU have condemned the ruling, alleging that the conviction is a ploy to keep the top opposition leader behind bars in order to keep her from elections; Yanukovych adamantly refuses to release her.

Tymoshenko is relying on getting her verdict overturned by the European Court of Human Rights, but Vlasenko has said the process could take 10 months, or longer, for the Strasbourg court to make a ruling in the case.

On Nov. 15, the Ukrainian parliament rejected a move to downgrade Tymoshenko's abuse-of-power conviction to a misdemeanor charge that would see her release, maintaining that the former prime minister overstepped her powers when she negotiated the Russia gas contract, which, ultimately, was deemed harmful for the Ukrainian economy.

Tymoshenko insists that the legal woes are a political lynching by her foe, Yanukovych, who wants to rid himself of a political rival. Last year, Tymoshenko lost to Yanukovych in a bitter battle for the presidency, garnering 45.47 percent of the votes.