Speaking to reporters in Kyiv ahead of his meeting on Friday with President Viktor Yanukovych, Westerwelle said Germany would continue to advocate for better treatment of Tymoshenko and her right to a fair trial.
"From our point of view, Mrs. Tymoshenko has full rights to an honest judicial hearing and decent medical treatment. The German proposal for medical monitoring and treatment [in Germany] remains on the table," Westerwelle said.
Tymoshenko, 52, has developed chronic back trouble since being jailed in October 2011 for a seven-year term, following an internationally-criticized trial on abuse of office charges linked to a gas deal she brokered with Russia in 2009.
Westerwelle, who met with Tymoshenko's daughter, Yevhenia (pictured above), and leaders of opposition parties before his talks with Yanukovych, condemned the use of "selective justice" in Ukraine.
"It is very important that 'selective justice' is not used in any system of values in Europe. It must not be allowed in either Europe or Ukraine," he said.
EU delays signing
The European Union has said Tymoshenko's jailing appears to be political vengeance. She was a leader of the Orange Revolution protests of 2004, which derailed Yanukovych's first bid for the presidency.
The EU has delayed signing a key trade agreement with Ukraine until Tymoshenko and several of her Cabinet allies are released. The agreement would serve as the first step towards potential membership of the EU.
In April, Europe's human rights court partly ruled against Ukraine on Tymoshenko's jailing. The court ruled unanimously that Ukraine had violated sections of the European Convention on Human Rights relating to liberty and security, speedy review of the lawfulness of detention, right to compensation for unlawful detention, and a limitation on restricting rights.
A majority also ruled that Ukraine had not violated a prohibition on inhuman or degrading treatment or punishment as Tymoshenko had alleged.
Tymoshenko herself had accused Ukraine's government of rigging the case against her and holding her under inhumane conditions.
jr/ipj (Reuters, dpa)