NEW YORK CITY-Silverstein Properties has bumped Marty Burger up from co-CEO to the sole executive in the position, effective immediately. Company founder and the former other co-CEO, Larry Silverstein, will step aside, becoming chairman of the firm.

Effective immediately, Burger will oversee the company's day-to-day operations and lead its efforts to develop new projects in the United States, China, Eastern Europe and Israel. For his part, Silverstein will continue to oversee development of the World Trade Center. A spokesman for the company declined to comment on the motivation behind the move, but Silverstein has said in recent comments that he's slowing down.

In making the announcement, Silverstein says, “I am delighted that Marty will lead Silverstein Properties as we continue to grow and explore exciting new possibilities throughout New York City, the nation and the world. Over the past four years, he has done an incredible job helping us expand our business globally. Thanks to his efforts, we have financed and built iconic development projects, acquired new properties and formed new joint ventures with top-tier partners across the U.S. and around the world.”