Apple Inc. has revised its iPhone delivery contracts with Japan's three largest mobile carriers after concerns arose that its restrictions on rate plans violated antitrust regulations, the country's antitrust watchdog said Wednesday.

The Japan Fair Trade Commission said it ended its probe into the issue as Apple and its Japanese arm have already agreed on new terms with NTT Docomo Inc., KDDI Corp. and SoftBank Corp.

Apple had asked the three companies to subsidize the retail prices of iPhones in the form of discounted rate plans, a stipulation the FTC saw as preventing the carriers from freely setting their prices and possibly hindering competition.

Last July, KDDI began offering plans that do not include subsidies for smartphones but instead charge a cheaper rate for long-term subscriptions. But because the plan conflicted with the agreement with Apple, KDDI could not offer it for iPhones, which are hugely popular in Japan with around half of market share, according to the FTC.

The FTC had been investigating the issue since October 2016 but deemed it resolved after Apple said earlier this month it would allow the three carriers to sell iPhones without subsidies.