NTT Docomo Inc., the nation's largest wireless operator, said a price war with other carriers and discounts on the latest iPhones may threaten its full-year forecast after adding the Apple Inc. devices to lure customers.

Curbing subsidies on mobile phones will give competitors an advantage as customers shop for the best deal, Chief Financial Officer Kazuto Tsubouchi said in an interview Thursday at the company's Tokyo headquarters. NTT Docomo is projecting operating profit of ¥840 billion in the 12 months ending March 31.

NTT Docomo added the iPhone 5s and 5c in September as it battles SoftBank Corp. and KDDI Corp. for subscribers amid an aging population. The move helped it add the most users in December, the first time it led monthly additions among wireless carriers since 2011, before its rivals fought back with new discounts.