Other guests include Samuel Eto'o, Abedi Pele and George Weah for the celebrations held this weekend.
"We have invited Lionel Messi and he accepted, now let's see if his schedule will allow him to make the trip. I'm confident he'd be around," Milla told reporters in Yaounde.
"He will be able to fly in with a private jet to feast with us. Cameroonians would be happy to see Messi here," he said.