MILAN — AC Milan goalkeeper Gianluigi Donnarumma will not extend his contract with the Serie A side, putting Europe’s elite clubs on alert.

Milan must now decide whether to sell the talented teenager before his current deal expires at the end of next season.

Milan CEO Marco Fassone announced the decision on Thursday after talks with Donnarumma’s agent Mino Raiola.

Fassone says “it is a definitive decision” and “it saddens us” but that “Milan will move forward.”

Donnarumma has been an ever present for Milan since October 2015, when he became the youngest goalkeeper to start a Serie A match, at the age of 16 years, 8 months, 6 days.

The 18-year-old Donnarumma, who has already made four international appearances, is seen as the heir to veteran Italy goalkeeper Gianluigi Buffon.