(Recasts with confirmation, reaction)

By Edith Honan

NEW YORK, Feb 27 (Reuters) - After 35 years on the job, Manhattan District Attorney Robert Morgenthau said on Friday he will not seek re-election to a position in which he has focused in recent years on prosecuting serious financial crimes.

Morgenthau, 89, has served as Manhattan district attorney longer than anyone else in history, outlasting countless actors who played the role of the D.A. in film and television dramas.

He said he will continue serving another 10 months until his current term ends.

"Some people are slow learners and it took me a long time to realize that I was getting older," Morgenthau said at a news conference announcing his decision.

He has been a fixture in the New York Democratic Party for decades. His father served as U.S. treasury secretary and his grandfather was ambassador to the Ottoman Empire.

Mayor Michael Bloomberg described him as "a New York Institution," saying, "few people have served the city longer or more ably." Police Commissioner Raymond Kelly said: "He's just an icon, he's a legend."

But Columbia Law School Professor Daniel Richman called Morgenthau's tenure a "mixed bag" whose work on white collar cases was often done "on the fly" and with an unclear agenda.