New Haven (AP) — Yale University President Richard C. Levin, who oversaw a big building and renovation program and expanded the school's financial aid programs, announced Thursday he is stepping down at the end of the academic year after 20 years at the Ivy League school.

Levin, 65, has served longer than any other president currently in the Ivy League or the 61-member Association of American Universities. He plans to take a sabbatical and write a book.

He is credited with leading the school's largest building and renovation program since the 1930s, expanding Yale's financial aid programs and international activities, improving the university's historically difficult relationship with its unions and building partnerships with New Haven.

"Rick Levin is simply one of the world's great leaders," Yale trustee Indra Nooyi, chief executive of PepsiCo, said in a statement. "He has been transformational in envisioning how a university should be a leading citizen in its home community and he has boldly staked out how the leading universities should become global institutions. His example has been a guide for how universities around the world can have a much greater impact."

Yale Corp., the university's governing body, will conduct a search.

Levin wrote in a message to the Yale community that he was looking forward to a sabbatical, "when at last I will have the time to complete a book of reflections on higher education and economic policy."