The 24-year-old has spent the last three seasons at CSKA Moscow and has impressed at the Russian giants.
"The president of CSKA has received the document with the proposal for Cearense," Amorim told Radio Globo.
Dudu has admitted he is flattered by the interest from Portsmouth, but that he will leave his future in the hands of CSKA.
"At this moment England has the most wealthy league in the world and I would be very happy to have the chance of playing there," said Dudu.
"For the moment I am under contract at CSKA for two more years so a transfer will only be possible if the officials of my current team agree that I can leave."