* Case strained ties with West; prison denies assault
* Merkel spokesman denies push for EU leaders to boycott matches
* Daughter says international reaction "incredible gift" (Adds German govt comment)
VIENNA, May 6 (Reuters) - Jailed Ukrainian former prime minister Yulia Tymoshenko is heartened by international support for her plight and will press on with her hunger strike against her treatment in prison, her daughter told an Austrian newspaper.
Tymoshenko, 51, has had an "enormous" psychological boost from the diplomatic backlash that has led to calls for politicians to boycott the Euro 2012 soccer championships in Ukraine, which will co-host the event with Poland, Oesterreich quoted Yevgenia Tymoshenko as saying.
Asked in the interview, published on Sunday, if Tymoshenko would continue the hunger strike she began on April 20, the daughter said:
"Yes, that is what she plans. She will continue her protest - with all the consequences - until decisions have been made. This is her intention and that is why I am afraid. I really fear for my mother's life."
The case has severely strained ties with the West. Some European politicians have cancelled plans to visit Ukraine on May 11 for a gathering on Central European issues in the southern resort of Yalta.
However, Chancellor Angela Merkel's spokesman denied a report in Spiegel magazine on Sunday that the German leader had pushed for all European Union leaders and heads of states to boycott tournament matches held in Ukraine.
Merkel would decide on whether to attend closer to the time, he said.
Tymoshenko, the main rival of President Viktor Yanukovich, was sentenced to seven years in prison last October for abuse of office after a trial the West says was politically motivated.
She is now in a prison in the city of Kharkiv, one of the tournament venues. She launched her hunger strike in protest at what she said was an assault by prison guards, an allegation denied by the prison administration.
Tymoshenko - who has complained for months of crippling back pain but refused treatment from Ukrainian medics - has agreed to accept treatment from a German doctor at a Ukrainian hospital, a doctor who saw her said last week.
Germany has been one of the toughest critics of the Kiev government and its treatment of Tymoshenko but looked to be striking a softer tone on Sunday.
"Quiet diplomacy is often more effective than loud declaration," Volker Kauder, head of Merkel's conservatives in parliament told the Neuen Osnabruecker Zeitung.
Foreign Minister Guido Westerwelle told Welt am Sonntag newspaper the most pressing issue was trying to find a way to get Tymoshenko effective medical care. With the engagement of a German doctor a vital first step had been made, he added.
Yevgenia said Tymoshenko, whom she visited last week, was pale and very thin after refusing food for two weeks.
"Of course I told her about the boycott. That gives her strength, helps her enormously psychologically. The global support makes her strong," she said.
"My mother had not expected this enormous international reaction, which came as an incredible gift. Of course she too does not want the country to be boycotted. This boycott affects the whole country. On the other hand the conditions in our country in the end have to be corrected." (Reporting by Michael Shields; additional reporting by Alexandra Hudson in Berlin; Editing by Alison Williams)