"It is not easy to leave Liverpool, but Villa are also a big club, so I'm happy to come here," he said.
"It is nice to be here and I am looking forward to making my debut on Saturday against Blackburn at Villa Park, when I will do my very best to open with a goal.
"I spoke to David O'Leary at length and he was a big factor in my deciding to come here.
"It was a big decision for me, but if the manager wants you it is easier and David's influence was one of the reasons I am here.
"I used to play alongside Patrik Berger at Liverpool and also with the Czech Republic. So I spoke to him and he said so many good things about Villa to encourage me to join."