Starting Thursday, Japan Communications will begin offerring a SIM card for unlocked iPhone 4 units sold in Japan by Softbank Corp, although the service plan costs 6,260 yen a month, while  the unlocked iPhone 4 will sell for about 60,000 yen at Japan Communications Inc.

Nikkei reports that Japan Communications Inc. announced Monday the start of a service that makes iPhone 4 compatible with NTT DoCoMo Inc.'s mobile network.

Officially distributed in Japan by Softbank Corp. with a locked SIM card, the iPhone 4 will be incompatible with rival networks.

As noted by the source, “The card is free, but a service plan costs 6,260 yen a month,” which translates into about $75.

The “unlocked” iPhone 4 will sell for about 60,000 yen (roughly $715), through Japan Communications.

Softbank is also making the iPhone 4 free for subscribers who sign up for a service contract. The operator is offering a 5,705 yen monthly plan.

People are likely to pay for the service because of the call quality on DoCoMo's network, Japan Communications believes.

In related news, a source from China Unicom has recently confirmed that iPhone 4 is launching on September 16 in the territory.

The carrier will include free cases for every customer.

Priced at $199 (US) for the 16GB model and $299 (US) for the 32GB model, iPhone 4 is currently available with a two-year contract in France, Germany, Japan, the UK and the US.

Similar prices apply for the additional 17 territories getting iPhone 4 on July 30, when Apple announced availability for the handset in Australia, Austria, Belgium, Canada, Denmark, Finland, Hong Kong, Ireland, Italy, Luxembourg, Netherlands, Norway, New Zealand, Singapore, Spain, Sweden and Switzerland.

iPhone 4 is set to launch in even more countries by the end of 2010.

Apple plans to announce availability and local pricing for these additional countries in an official report.