Following Quique Setien's sacking at the beginning of the week, Koeman was appointed as Barcelona's new manager on Wednesday afternoon.
The former Netherlands boss arrives on the back of a tumultuous season that saw the club fail to win any silverware for the first time since the 2007/08 campaign.
Barca's poor showings on the pitch in recent times have been compounded by a spate of off-field distractions, all of which have reportedly resulted in star player Messi requesting to leave.
In his first press conference since returning to the Camp Nou, Koeman addressed the issue of the 33-year-old's future and admitted that nothing had yet been decided.
"I don't know if I have to convince Messi [to stay] or not. You want to have the best [players] in the world in your team, not the opposite," he said.
"I want to work with Messi. He wins you games and, if he provides the performances he has always shown, I'll be happy if he wants to stay.
"He has a contract and I have to talk to him, because he is the captain of the team. We are going to work and talk with several players and in the case of Messi, I hope that he will be here for many more years.
