NTT East Corp. and NTT West Corp. are contemplating deeper workforce "cuts" because the popularity of mobile phones and a future obligation to reduce the fees it charges other carriers are eating into their profitability, officials said Friday.

The two domestic arms of Nippon Telegraph and Telephone Corp. now intend to ask up to 6,500 employees to leave in fiscal 2000 and fiscal 2001 on a voluntary basis, expanding a plan they announced last November to cut as many as 21,000 workers over three years, the officials said.

The firms will consult their labor unions after hammering out the details of the plan, the officials said.