Polish President Aleksander Kwasniewski said he has been invited to visit Ukraine to mediate in a political crisis in the wake of a presidential election called fraudulent by international observers and the European Union. Official election results show liberal opposition presidential candidate Viktor Yushchenko was defeated by Moscow-backed candidate Prime Minister Viktor Yanukovich. Yushchenko, flanked by thousands of protesters, says he has evidence of stolen votes that he said robbed him of victory. Kwasniewski has close personal ties with outgoing Ukrainian President Leonid Kuchma and is also a leading advocate of Ukraine's closer ties with the west, including potential EU membership. "I have been invited by both Yushchenko and Kuchma to come to Kiev but no decision has been made, because I should go only when there is material for a serious discussion," Kwasniewski told reporters. He said a working group of Polish diplomats and his advisers were leaving for Kiev for preparatory talks.