Polish sports minister Miroslaw Drzewiecki said Poland would do everything it could to host the tournament with Ukraine.
"Ukraine is the only partner for us, it can count on our full support and cooperation," Drzewiecki said in a statement.
"We will do everything to ensure that the tournament is a joint success of both Poland and Ukraine."
Hryhoriy Surkis, chief of Ukraine's football federation, said the two countries have increased their cooperation.
"Neither the Ukrainian nor Polish side recommended hosting Euro 2012 solely in Ukraine or Poland," he said.