Manucho, currently in Angola with the national team, said: "The club is dealing with the work-permit process. I have been asked to turn up on July 1 for pre-season.
"Since the end of the Greek league, I have been in contact with (United assistant manager Carlos) Queiroz and I know that things are going well.
"I am not thinking about wearing a shirt other than that of United. I am just thinking about playing in the Champions League next season."
United boss Sir Alex Ferguson revealed in February the club was keen to hang on to Manucho after he impressed at the African Nations Cup, scoring four goals.
Ferguson said: "Given that he played for Angola and did so well at the Africa Cup of Nations, we will reapply for his work permit in the summer and hopefully next year he could play for us."
Manucho also claimed Panathinaikos would have got more out of him had he been given more regular run-outs.
He added: "It was a good experience (in Greece). Had I played more games, I believe I could have scored more goals and silenced those who still doubt my qualities.
"Overall, it was a positive experience. English and Greek football have different styles though."