Doctors in Austria say they are winding up tests on Ukraine's opposition leader Viktor Yushchenko and will reveal the cause of the mysterious illness that disfigured his face later in the day (Saturday).

The doctors at a leading hospital (Rudolfinerhaus) in Vienna say they have checked the size and functioning of Mr. Yushchenko's vital organs to see what kind of damage might have been done. The say they ran new blood tests to check for any signs of poisoning.

Mr. Yushchenko became ill in September. He has consistently claimed he was poisoned in the run-up to November's disputed presidential election. Ukraine's Supreme Court voided the outcome on grounds of widespread fraud. According to those results, Prime Minister Viktor Yanukovych won the vote.

A court-ordered repeat of the run-off election is set for December 26th. Mr. Yanukovych, who fears the new vote will not be fair, has asked Mr. Yushchenko to debate.