The club is desperate to keep hold of the five-time World Player of the Year, whose deal expires in 2018.
"Leo Messi is the best (player) in the history of football and we want him to stay with us," Bartomeu told reporters on Tuesday.
"There will be negotiations...but even if I don't want to talk about figures, if he's the best player in the world it makes sense that he is so from all points of view."
After extending the contracts of Neymar and Luis Suarez until 2021, Barca are desperate to keep hold of the five-time World Player of the Year, whose deal expires in 2018.
"He's at home here...I believe Leo is fully convinced he's in the best place he can be," said Bartomeu.
It's been a tumultuous year for Messi off the pitch though, with him and his father sentenced to 21 months in jail for tax fraud.
The pair have appealed the ruling, although the prison sentences are likely to be suspended as is common in Spain for first offences for non-violent crimes carrying a sentence of less than two years.
"I don't believe these tax affairs will have an influence (on a contract extension)...because Leo knows, I know and we all know he hasn't done anything wrong," added Bartomeu.
The Barca president also expressed his desire to see the 29-year-old finish his career at the Camp Nou.
"It would be a story to tell future generations," said Bartomeu. "We had the best player in the world and he played here all his life."
He confirmed Barca were keen as well to extend the contracts of captain Andres Iniesta, Croatia midfielder Ivan Rakitic and goalkeeper Marc-Andre ter Stegen in addition to coach Luis Enrique.
"Towards April we'll speak about the coach. For now we're focused on the competition...but we would like him to stay," Bartomeu said of Enrique, who is out of contract at the end of June.