Japan Post Service Co., the mail-delivery arm of the Japan Post group, plans to lay off some nonregular workers when their contracts expire at the end of March as part of efforts to turn its business around, sources said Saturday.

The unit has approximately 160,000 nonregular employees nationwide, and the contracts of as many as "several thousand" may not be renewed, including those who deliver and sort mail, the sources said.

Japan Post Service promoted about 6,500 nonregular workers to regular status in December as part of a plan to review the postal service privatization and seek to stabilize the employment of nonregular staff.

A labor union source said the shift in personnel policy within such a short period of time could disrupt the workplace and possibly interfere with business operations.

Japan Post Service is currently soliciting voluntary retirement among its nonregular workers.

It will soon start holding interviews with the workers to ask them to reduce their work days or hours starting in April, and if they don't agree it will tell them their contracts won't be renewed at the end of March, the sources said.

The cuts come after the carrier plunged into the red in the first half of fiscal 2010 with an operating loss of ¥92.8 billion from losses due largely to delivery delays resulting from the integration of its Yu-Pack parcel delivery business with that of Nippon Express Co.