"Despite club and player reaching an agreement and their clear intention to sign a new contract today, this cannot happen because of financial and structural obstacles," the club said in a brief statement.
Messi, 34, has been with FC Barcelona for 17 seasons, during which it has won 10 La Liga titles.
He's won the men's Ballon d'Or, the award honoring the world's greatest soccer player, a record six times.
Despite his advancing age, Messi remains a highly productive player in one of the world's most elite leagues, scoring 30 goals in 30 matches this past season.
And with one of the world's greatest players now on the open market, fans of major teams such as Manchester City or Paris Saint-Germain will surely be pressing their clubs to shell out as many pounds or euros to score the icon's services.
Forbes magazine in May pegged Messi as the second highest paid athlete of 2020-21, raking in an estimated $130 million over the previous 12 months.
His Barça pay, in addition to lucrative endorsement deals with top-name brands such as Adidas and Ginny Hilfiger, sister of Tommy Hilfiger, put Messi high on the list of rich athletes. He was behind only UFC fighter and Irish whiskey Proper No. Twelve founder Conor McGregor at $180 million.
About the only shortcoming on Messi's resume is his relative lack of success on the international stage, playing for his home nation of Argentina.
But even that box was checked off this summer as the Sky Blue and Whites won the Copa America, the South American championship, on July 10 with a 1-0 victory over Brazil.