It's really happening.

Lionel Messi told Barcelona officials Tuesday he intends to terminate his contract and leave the club this summer, sources told Sam Marsden and Moises Llorens of ESPN.

Messi informed the club of his decision via fax, according to Sid Lowe of The Guardian.

The 33-year-old icon has a contract until 2021, but he's grown increasingly frustrated by the worsening state of affairs at the Camp Nou. Barca's humiliating 8-2 defeat to Bayern Munich in the Champions League quarterfinals capped the side's first season without a trophy since 2007-08, and it appears to have been the final straw in convincing the Argentine it's time to move on from the club he joined as a teenager in 2001.

Messi's contract reportedly contains a clause that allows him to unilaterally terminate his deal with the Catalan side at the end of the season. Barcelona, however, insist the clause expired in June, according to Fabrizio Romano of The Guardian.

Various reports in Spain suggest Messi believes the clause is valid through the end of August because the 2019-20 campaign was prolonged due to the coronavirus pandemic.

Barcelona officials will meet in the coming days to discuss the matter, Romano reports, but the club remains adamant Messi will only leave if an interested team satisfies his mammoth €700-million release clause.

The Spanish giants have publicly maintained that the decorated forward will continue to be the pillar of the team under Ronald Koeman since the Dutchman replaced Quique Setien as manager earlier in August. But reports indicate various board members have privately entertained the idea of selling the generational talent in the hopes of reinvesting and rebuilding an aging squad.

It was reported earlier in August that Messi told Koeman he had doubts about his future when the two met to discuss plans for the upcoming season.

It remains to be seen how many clubs could actually afford to sign the six-time Ballon d'Or winner if they need to pay a transfer fee. Manchester City are reportedly "crunching the numbers" to see if a deal is financially viable, while rumblings of Inter Milan's interest persist.

But if Messi does indeed terminate his contract and becomes a free agent, countless other teams will instantly thrust themselves into competition for his services.

Messi, who has been involved in public disputes with the Barca brass in recent months, seems acutely aware he's running out of time to add to his four Champions League titles, especially with Barcelona on the verge of a significant rebuild.