Manhattan's longtime district attorney, Robert M. Morgenthau, has decided not to seek reelection this year, several New York newspapers reported on their Web sites Friday.

Morgenthau, 89, has been a major force in New York's legal community for decades, serving as U.S. Attorney for the Southern District of New York and winning nine consecutive terms as Manhattan's district attorney.

"The challenge of his successor will be to fill the shoes of a giant," said Charles A. Stillman of Stillman, Friedman & Shechtman PC.

The New York Times and the New York Post, citing sources, reported Morgenthau has decided not to run again. The Post, citing sources, reported that Morgenthau has been privately telling top deputies in his office the news and is expected to make his intentions public in the next few weeks.

Morgenthau scheduled a press conference for 4:15 p.m. EST on Friday but didn't indicate the topic of the press conference.

A spokeswoman for Morgenthau's office didn't immediately have a comment Friday.

Morgenthau began his legal career in 1948 after graduating from Yale Law School, joining Patterson, Belknap, Webb & Tyler LLP.

After 12 years of practicing corporate law, he was appointed U.S. Attorney for the Southern District of New York in 1961 and created its much-touted securities fraud unit.

Morgenthau resigned as U.S. Attorney in 1970 and won his first election as district attorney in 1974.

As district attorney, Morgenthau greatly increased the reach and breadth of the office, including pursuing international prosecutions, Stillman said.

Stillman represented Mark H. Swartz, former Tyco International Ltd. (TYC) chief financial officer, on charges Swartz and ex-Tyco Chief Executive L. Dennis Kozlowski looted the company in a case brought by Morgenthau's office.

Morgenthau also influenced pop culture, serving as the model for the character of Adam Schiff, the original district attorney on NBC's long-running television series "Law & Order."

"[Morgenthau's] had a long history with the office, as well as U.S. attorney," said Mark C. Zauderer of Flemming Zulack Williamson Zauderer LLP. "There are some able and experienced people who are contending for the position."

Leslie Crocker Snyder, a former judge who has previously challenged Morgenthau, is one potential candidate for the office.

Cyrus Vance Jr., the son of Jimmy Carter's secretary of state and a former prosecutor, and Richard Aborn, another former prosecutor, also have been raising money for a potential run.

Vance and Aborn both said Friday that they planned to enter the race for district attorney if Morgenthau doesn't seek another term.

Snyder didn't immediately return a call for comment.

-By Chad Bray, Dow Jones Newswires; 212-227-2017; chad.bray@dowjones.com