* Row over imprisoned ex-PM prompts stay-away

   * At least eight presidents said they would boycott meeting

   * Polish leader planned to urge Yanukovich to soften law

KIEV - Ukrainian President Viktor Yanukovich on Tuesday called off a regional summit rather than host a partly-boycotted meeting and face a lecture over his treatment of imprisoned opposition leader Yulia Tymoshenko.

The foreign ministry's announcement of the cancellation of the talks, planned for Thursday and Friday in Yalta, was an embarrassing setback for Yanukovich and a triumph for Tymoshenko, on hunger strike in prison in the city of Kharkiv.

The presidents of Germany, Austria, Italy, Croatia, Estonia, Slovenia, Bulgaria and the Czech Republic had all said they were pulling out of the informal summit which was attended by 20  heads of state when it was held in Poland last year.

The boycott followed allegations by Tymoshenko, a former prime minister, that she was beaten by prison guards last month.

The authorities have denied any mistreatment of the charismatic Tymoshenko, who was a driving force in the 2004 Orange Revolution street protests which doomed Yanukovich's first bid for the presidency.

But the boycott threat, and the cancellation of the Yalta gathering, highlight Ukraine's growing isolation as it prepares to host European soccer championships from June 8 to July 1.

"Due to the inability of some European state leaders to take part in the summit ... Ukraine considers it sensible to delay it," the ministry said in a statement. It said new dates for the gathering would be announced later.

 UNWELCOME ADVICE

With the Tymoshenko case likely to loom large in off-the-agenda conversation, Yanukovich may have anticipated unwelcome advice from some of those attending the annual regional gathering, which looks at eastern European countries' progress towards European integration.

Polish President Bronislaw Komorowski, whose country is co-hosting the Euro-2012 soccer tournament with Ukraine next month, had served notice he intended to raise Tymoshenko's case.  

"President Komorowski was planning to go to Yalta to appeal to President Yanukovich for changes in the Ukrainian laws that would make sentencing for political activity on the basis of criminal law impossible," Komorowski's spokeswoman Joanna Trzaska-Wieczorek said in Warsaw.

The EU and the United States have denounced Tymoshenko's trial and seven-year sentence for alleged abuse of power as politically motivated, and urged Yanukovich to free her.

But, with some European leaders also threatening to stay away from the soccer tournament, he has refused to intervene in what he says is a decision by an independent court.

Instead, authorities have brought to court fresh tax evasion charges against her which carry a sentence of up to 12 years.

The decision to call off the Yalta meeting marked another PR coup for Tymoshenko, Yanukovich's nemesis, who has often managed to put him on the back foot by keeping an international focus on her plight from her prison bed.

Tymoshenko, 51, has been on hunger strike since April 20 in protest at her alleged ill-treatment in prison.

The authorities have refused to allow her to take up an offer from Germany to be treated in Berlin for chronic back trouble. Under a deal worked out involving German doctors, she had been tentatively expected to move to a Kharkiv hospital on Tuesday to be treated there.

   WEDNESDAY MOVE?

However, after meeting a German doctor in prison, she declined to be moved from Kharkiv's Kachanivska prison to hospital on Tuesday, though she left open the prospects of transferring there on Wednesday.

Tymoshenko needed more time to discuss her situation with her lawyers, a prison service statement said.  

If she did make her much-publicised move to hospital on Wednesday, this could again upstage Yanukovich, since May 9 is Victory Day when he will lead the country in ceremonies marking the Soviet Union's defeat of Nazi Germany.

 One immediate question was whether she would maintain her hunger strike while being treated by the German doctors.

 "She has not abandoned her hunger strike and she will not abandon it until the question of her situation has been resolved," one of her lawyers, Olexandr Plakhotnyuk, told reporters outside the prison on Tuesday.

"She is drinking only water. What will take place next will be decided after she meets doctors today."

Plakhotnyuk said her health had worsened because of the hunger strike. "Her blood pressure has dropped and I was there when they took her temperature. It was 35.7," he said.