German President Joachim Gauck has canceled a planned visit to Ukraine next month amid concerns over the health and treatment of jailed former Ukrainian Prime Minister Yulia Tymoshenko.
A spokesman confirmed Gauck has nixed plans to attend a gathering of central European heads of state in the Black Sea resort of Yalta in May.
The "Suddeutsche Zeitung" daily said Gauck took the decision after consultations with Chancellor Angela Merkel.
Tymoshenko is serving a seven-year prison sentence for abuse of office and is currently facing a separate trial for alleged tax fraud.
Tymoshenko says she is the victim of political vendetta by President Viktor Yanukovych, whose initial presidential bid was thwarted by the 2004-05 Orange Revolution but who defeated Tymoshenko in a presidential election in 2010.
She began a hunger strike on April 20, accusing prison guards of mistreatment.
Tymoshenko's imprisonment has badly strained relations between Ukraine and the European Union.
Based on reporting by Reuters and Deutsche Welle