Ukraine has decided to postpone the 18th summit of Central European states planned for 11-12 May in Yalta after several of European leaders said they would boycott it.
Europe-wide concern about the treatment of jailed Ukrainian opposition leader Yulia Tymoshenko prompted the boycott. Yalta was the 11-12 May summit venue.
Former PM Yulia Tymoshenko has chronic back pain and is on hunger strike.
The presidents of Germany, Austria, Romania and the Czech Republic were among those who cancelled their trips.
Ukraine has not set a new date yet. There is also a threat that leaders may boycott Euro 2012 football matches in Ukraine next month.
Ukrainian Foreign Ministry spokesman Oleksandr Dykusarov said: “As a number of European heads of state cannot take part in the 18th summit of Central European states, Ukraine deems it necessary not to hold the summit on 11-12 May in Yalta.”
Yulia Tymoshenko is in jail in the eastern city of Kharkiv and on Tuesday she refused to be moved to a local hospital.
She has alleged that prison guards beat her during a previous attempt to move her to hospital and her supporters released photographs showing bruises on her body.
Ukraine denies her allegations, including her claim that she is being punished as an act of political revenge by President Viktor Yanukovych.
Yulia Tymoshenko was jailed for seven years in October 2011 for abuse of office during her time as prime minister. She is an arch-rival of Viktor Yanukovych, whom she helped oust from power in the 2004 Orange Revolution.
Viktor Yanukovych had been elected president in a rigged election. However, in 2010 he staged a political comeback, defeating Yulia Tymoshenko in a new presidential election.