BOSTON, USA: George Nolen, the head of Siemens AG's U.S. operations is planning to retire at the end of the month, a spokeswoman for the German conglomerate said on Thursday.

A 26-year Siemens veteran George Nolen, 53, became president and chief executive of Siemens' U.S. arm in January 2004, according to the company's website.

A successor has not yet been named, Siemens spokeswoman Christine Alvarado said.