NTT DoCoMo is rumored to be launching a mobile virtual network in the U.S. that will ride either T-Mobile or AT&T’s wireless network. The company wants to launch this to push its iMode mobile Internet service in the U.S. For me, that is too little, too late. It is hard to imagine any takers for iMode in a post-iPhone, web-centric mobile world.

DoCoMo was once viewed as a pioneer in the wireless world, thanks to its groundbreaking iMode service. The service made Japan, NTT’s home base, the envy of every other country on the planet. Smart-ish phones, smart services, mobile commerce — NTT DoCoMo seemed to have it all.

Except one thing — it didn’t know how to deal with market saturation. Since it was making hand over fist, the company tried to expand overseas, buying shares in American, European and Asian telecom operators. Those early attempts didn’t work out well, and neither will this one. NTT DoCoMo has trailed upstart Softbank in net new subscriptions this past month.